docs: bali fixture corpus, and AR-004 blocks reproducible fixtures

Records `bali/` — five ~77s clips of Road to Bali (1952) — as the fixture
source. Public domain, which is the point rather than a convenience: derived
fixtures can be committed, where anything cut from a copyrighted title could
not live in the repository at all.

Makes explicit what the tier table only implied: CI never calls a model. Not a
preference — the embedder measures ~930 ms/frame on the CPU provider, so a 77s
clip at 5 fps is six minutes of inference. Every model invocation happens
locally and CI consumes the result as data, which is what makes the T1/T2 split
load-bearing rather than stylistic.

Two properties of the corpus to design around: 480x360 puts many faces below
the AR-002 66px minimum, so generation must set and record --min-face-px; and
77s at 1 fps is too thin to exercise an extinction window measured in tens of
seconds, so fixtures want 5 fps.

The finding that matters: a trial dump produced 49 frames of an expected ~385,
stopping at 51s of 77s, with 285 frames dropped at camera_pos and 51 at
face_aligner on channel overflow. Channels drop rather than block, and what
drops depends on timing, so the same command twice can yield different dumps.
Golden fixtures cannot be built on that — AR-004 is a prerequisite for VR-001
fixtures, not just a throughput concern for crowd scenes.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

TRACES: AR-004, VR-001 | PR-002

docs/requirements.md

@@ -213,6 +213,46 @@ structurally unverifiable on the CI host. It needs a GPU host and a synthetic
 large gallery, so it is the requirement most likely to silently regress. Its
 benchmark (VR-008) should run on a schedule rather than on demand.
 
+### CI never calls a model
+
+**Not "should not" — cannot.** The N100 has no GPU, and even the ONNX Runtime CPU
+provider is impractical: a measured run of the embedder on this hardware sits at
+~930 ms per frame, so a 77 s clip at 5 fps would take roughly six minutes of
+inference alone. Every model invocation therefore happens **locally, ahead of
+time**, and CI consumes the result as data.
+
+This is what makes the T1/T2 split load-bearing rather than a preference: T1 and
+T2 are the only tiers that can exist in CI at all.
+
+### Fixture corpus — `bali/`
+
+Five clips of **Road to Bali (1952)**, ~77 s each, 480×360, 30 fps, 42 MB total.
+
+Public domain, and that is the reason to use it rather than a convenience:
+**derived fixtures — dumps, crops, golden outputs — can be committed without the
+rights question that rules out sharing gallery data (SR-005).** A fixture cut
+from a copyrighted title could not live in the repository at all.
+
+Two properties to design around rather than discover:
+
+- **480×360 means small faces.** At this resolution a face is often 40–80 px, so
+  the AR-002 minimum of 66 px (original resolution) rejects much of what is
+  there. Fixture generation must set `--min-face-px` explicitly and record it,
+  or the dumps will be sparse for reasons unrelated to what is being tested.
+- **77 s is short.** At 1 fps that is 77 frames — too thin to exercise an
+  extinction window measured in tens of seconds. Generate at 5 fps (≈385 frames,
+  ~1 MB) and record the rate in provenance, since the behaviour under test
+  changes with it.
+
+> **AR-004 blocks reproducible fixture generation.** A trial run of one clip
+> produced 49 frames of an expected ~385, ending at 51 s of 77 s, with the
+> diagnostics reporting 285 frames dropped at `camera_pos` and 51 at
+> `face_aligner`. Channels overflow and **drop** rather than blocking, and what
+> gets dropped depends on timing — so the same command run twice can produce
+> different dumps. Golden fixtures cannot be built on that. AR-004 is therefore
+> a prerequisite for VR-001 fixtures, not merely a throughput concern for crowd
+> scenes.
+
 ### Fixtures — precomputed inference, pulled by CI
 
 The N100 cannot run inference at any useful rate, so **inference output is

docs/traceability.md

@@ -3,7 +3,7 @@
 <!-- GENERATED FILE - do not edit by hand. -->
 <!-- Regenerate: scripts/traceability/traceability-gate.sh -->
 
-**Generated:** 2026-07-31T08:01:31+00:00
+**Generated:** 2026-07-31T08:10:51+00:00
 
 Denominators are read from [`requirements.md`](requirements.md) at run time, never hardcoded. Coverage counts a requirement only when it is tagged in source **and** has a verification tier this repo's CI host can execute (`T1, T2, T3, static`).
 
@@ -12,12 +12,12 @@ Denominators are read from [`requirements.md`](requirements.md) at run time, nev
 | Metric | Value |
 |---|---|
 | Source files scanned | 95 |
-| TRACES tags found | 82 |
+| TRACES tags found | 90 |
 | EXCEPTION tags found | 0 |
 | Requirements defined | 63 |
-| Requirements covered | 24 |
-| **Coverage** | **38.1%** (24/63) |
-| Coverage of CI-executable scope | 46.2% (24/52) |
+| Requirements covered | 26 |
+| **Coverage** | **41.3%** (26/63) |
+| Coverage of CI-executable scope | 50.0% (26/52) |
 | Tagged but unexecuted in CI | 3 |
 | Orphan tags | 0 |
 
@@ -27,7 +27,7 @@ Denominators are read from [`requirements.md`](requirements.md) at run time, nev
 |---|---|---|---|
 | AR | 13 | 0 | 27 |
 | DP | 2 | 0 | 8 |
-| IR | 6 | 0 | 8 |
+| IR | 8 | 0 | 8 |
 | GR | 3 | 0 | 9 |
 | VR | 0 | 3 | 11 |
 
@@ -88,12 +88,12 @@ _None._
 | AR-009 | Done | T2 | SR-002 | untagged | - | Camera-cut detection (histogram) as an association hint |
 | AR-010 | **Not started** — `… | T2 | SR-002 | untagged | - | Scene-boundary detection (TransNetV2) as an association hint |
 | AR-011 | Planned | T1, T2 | SR-002 | untagged | - | **Every model is fed the input it was trained for** — cost reduced by… |
-| AR-012 | **Done** — `src/tra… | T2 | **SR-002** | covered | `src/main.cpp`, `src/track_registry.hpp`, `tests/test_track_registry.cpp` | Presence follows **track extent**, not per-frame recognition |
+| AR-012 | **Done** — `src/tra… | T2 | **SR-002** | covered | `src/main.cpp`, `src/nodes/identity_matcher_node.hpp`, `src/nodes/result_sink_node.hpp`, `src/track_registry.hpp`, `tests/test_track_registry.cpp` | Presence follows **track extent**, not per-frame recognition |
 | AR-013 | **Done** — `last_se… | T2 | SR-002 | covered | `src/track_registry.hpp`, `tests/test_track_registry.cpp` | `last_seen` optional state machine; window ends at last sighting, nev… |
 | AR-014 | **Done** — swap clo… | T2 | SR-002 | covered | `src/track_registry.hpp`, `tests/test_track_registry.cpp` | Belief swap A→B terminates the track and starts a new one |
 | AR-015 | **Done** — reverse … | T2 | SR-002 | covered | `src/track_registry.hpp`, `tests/test_track_registry.cpp` | Two live tracks owned by one actor ⇒ treat as a detected cut, re-asso… |
-| AR-016 | **Done** — `flush()… | T2 | SR-002 | covered | `src/track_registry.hpp`, `tests/test_track_registry.cpp` | All tracks closed at EOF — a film ends with faces on screen |
-| AR-017 | **Done** — `DeadTra… | T1, T2 | SR-002 | covered | `src/track_registry.hpp`, `tests/test_track_registry.cpp` | Every presence claim carries its belief and identification route |
+| AR-016 | **Done** — `flush()… | T2 | SR-002 | covered | `src/main.cpp`, `src/nodes/result_sink_node.hpp`, `src/track_registry.hpp`, `tests/test_track_registry.cpp` | All tracks closed at EOF — a film ends with faces on screen |
+| AR-017 | **Done** — `DeadTra… | T1, T2 | SR-002 | covered | `src/nodes/result_sink_node.hpp`, `src/track_registry.hpp`, `tests/test_track_registry.cpp` | Every presence claim carries its belief and identification route |
 | AR-018 | Planned | T1, T2 | SR-005 | untagged | - | Per-subject embedding store with banded admission (novel enough, safe… |
 | AR-019 | In Progress | T2 | SR-005 | untagged | - | Per-film gallery annex from owned tracks; acquires the non-frontal vi… |
 | AR-020 | Planned | T2 | SR-005 | untagged | - | Deferred re-identification of unknown tracks against the final expand… |
@@ -101,7 +101,7 @@ _None._
 | AR-022 | Planned | T1, T2 | §4 | untagged | - | Capture still-unidentified tracks: embeddings, metadata, **context cr… |
 | AR-023 | Done | T1 | SR-002 | covered | `src/gallery/gallery_calibration.hpp`, `src/nodes/identity_matcher_node.hpp` | Fit sigmoid calibration from intra/inter similarity distributions |
 | AR-024 | **Done** — associat… | T1, static | SR-002 | covered | `src/config.hpp`, `src/evidence_discount.hpp`, `src/gallery/gallery_calibration.hpp`, `src/main.cpp`, `src/nodes/face_tracker_node.hpp`, `src/nodes/identity_matcher_node.hpp` | **Always the calibrated probability, never a raw cosine** — exception… |
-| AR-025 | **Done** — log-odds… | T1 | SR-002 | covered | `src/evidence_discount.hpp` | Per-track Bayesian accumulation in log-odds, with correlated-observat… |
+| AR-025 | **Done** — log-odds… | T1 | SR-002 | covered | `src/evidence_discount.hpp`, `src/nodes/identity_matcher_node.hpp` | Per-track Bayesian accumulation in log-odds, with correlated-observat… |
 | AR-026 | In Progress | T1, T4 | SR-001 | untagged | - | All similarity computed as GEMM, including annex and deferred pass |
 | AR-027 | Planned | T4 | SR-001 | untagged | - | Throughput acceptable for **arbitrary** gallery size |
 | DP-001 | Done | T1, manual | PR-004 | covered | `src/main.cpp` | One analysis core; modes are front-ends and must not fork pipeline lo… |
@@ -113,8 +113,8 @@ _None._
 | DP-007 | Planned | T1, manual | PR-004 | untagged | - | CI builder image, CPU-only, pinned by tag in the Gitea container regi… |
 | DP-008 | Planned | T1, manual | PR-004 | untagged | - | Builder images + release jobs per backend (cpu / cuda / rocm); ship b… |
 | IR-001 | Done | T1 | SR-003 | covered | `src/nodes/result_sink_node.hpp` | Emit the JRay truth format as sibling `.jray.json` |
-| IR-002 | Planned | T1 | SR-003 | untagged | - | Windows carry belief + route; `extraction.*` carries `extinction_sec`… |
-| IR-003 | Planned | T1 | SR-003 | untagged | - | Output written **after** the deferred pass, not at EOF |
+| IR-002 | **Done** — `schema_… | T1 | SR-003 | covered | `src/config.hpp`, `src/main.cpp`, `src/nodes/result_sink_node.hpp` | Windows carry belief + route; `extraction.*` carries `extinction_sec`… |
+| IR-003 | **In Progress** — s… | T1 | SR-003 | covered | `src/main.cpp` | Output written **after** the deferred pass, not at EOF |
 | IR-004 | **Done** — `src/aud… | T1 | SR-003 | covered | `src/audio_signature.cpp`, `src/audio_signature.hpp`, `tests/test_audio_signature.cpp` | Compute the audio signature exactly per server spec §3 |
 | IR-005 | **Done** — `tests/f… | T1 | SR-003 | covered | `src/audio_signature.cpp`, `src/audio_signature.hpp`, `tests/test_audio_signature.cpp` | Golden-vector fixture shared with the plugin repo to prove bit-exactn… |
 | IR-006 | Done | T1, manual | SR-001 | covered | `scripts/run_from_jellyfin.py` | Jellyfin round-trip: pull pending queue, push complete results only |
@@ -159,7 +159,7 @@ _None._
 
 **Locations:** 3
 
-- [`src/config.hpp:97`](../src/config.hpp#L97) — `Unknown`
+- [`src/config.hpp:103`](../src/config.hpp#L103) — `Unknown`
 - [`src/main.cpp:199`](../src/main.cpp#L199) — `reg_cfg, EvidenceDiscounter(same_person));`
 - [`src/nodes/face_tracker_node.hpp:2`](../src/nodes/face_tracker_node.hpp#L2) — `Unknown`
 
@@ -167,15 +167,20 @@ _None._
 
 **Locations:** 3
 
-- [`src/config.hpp:97`](../src/config.hpp#L97) — `Unknown`
+- [`src/config.hpp:103`](../src/config.hpp#L103) — `Unknown`
 - [`src/main.cpp:199`](../src/main.cpp#L199) — `reg_cfg, EvidenceDiscounter(same_person));`
 - [`src/nodes/face_tracker_node.hpp:2`](../src/nodes/face_tracker_node.hpp#L2) — `Unknown`
 
 ### AR-012
 
-**Locations:** 3
+**Locations:** 8
 
 - [`src/main.cpp:199`](../src/main.cpp#L199) — `reg_cfg, EvidenceDiscounter(same_person));`
+- [`src/main.cpp:216`](../src/main.cpp#L216) — `reg_cfg, EvidenceDiscounter(same_person));`
+- [`src/nodes/identity_matcher_node.hpp:119`](../src/nodes/identity_matcher_node.hpp#L119) — `const GalleryCalibration& calibration() const { return cal_; }`
+- [`src/nodes/identity_matcher_node.hpp:242`](../src/nodes/identity_matcher_node.hpp#L242) — `Unknown`
+- [`src/nodes/result_sink_node.hpp:49`](../src/nodes/result_sink_node.hpp#L49) — `static constexpr std::string_view label() { return "result_sink"; }`
+- [`src/nodes/result_sink_node.hpp:161`](../src/nodes/result_sink_node.hpp#L161) — `struct ActorMeta { std::string name, imdb_id, tmdb_id, jellyfin_id; };`
 - [`src/track_registry.hpp:2`](../src/track_registry.hpp#L2) — `Unknown`
 - [`tests/test_track_registry.cpp:3`](../tests/test_track_registry.cpp#L3) — `Unknown`
 
@@ -202,15 +207,18 @@ _None._
 
 ### AR-016
 
-**Locations:** 2
+**Locations:** 4
 
+- [`src/main.cpp:216`](../src/main.cpp#L216) — `reg_cfg, EvidenceDiscounter(same_person));`
+- [`src/nodes/result_sink_node.hpp:63`](../src/nodes/result_sink_node.hpp#L63) — `void set_pre_write_hook(std::function<void(double)> fn) { pre_write_ = std::move(fn); }`
 - [`src/track_registry.hpp:2`](../src/track_registry.hpp#L2) — `Unknown`
 - [`tests/test_track_registry.cpp:3`](../tests/test_track_registry.cpp#L3) — `Unknown`
 
 ### AR-017
 
-**Locations:** 2
+**Locations:** 3
 
+- [`src/nodes/result_sink_node.hpp:49`](../src/nodes/result_sink_node.hpp#L49) — `static constexpr std::string_view label() { return "result_sink"; }`
 - [`src/track_registry.hpp:2`](../src/track_registry.hpp#L2) — `Unknown`
 - [`tests/test_track_registry.cpp:3`](../tests/test_track_registry.cpp#L3) — `Unknown`
 
@@ -220,24 +228,26 @@ _None._
 
 - [`src/gallery/gallery_calibration.hpp:2`](../src/gallery/gallery_calibration.hpp#L2) — `Unknown`
 - [`src/gallery/gallery_calibration.hpp:53`](../src/gallery/gallery_calibration.hpp#L53) — `float boundary_at(float p = 0.5f, float log_prior_odds = 0.f) const`
-- [`src/nodes/identity_matcher_node.hpp:110`](../src/nodes/identity_matcher_node.hpp#L110) — `const GalleryCalibration& calibration() const { return cal_; }`
+- [`src/nodes/identity_matcher_node.hpp:111`](../src/nodes/identity_matcher_node.hpp#L111) — `const GalleryCalibration& calibration() const { return cal_; }`
 
 ### AR-024
 
 **Locations:** 6
 
-- [`src/config.hpp:97`](../src/config.hpp#L97) — `Unknown`
+- [`src/config.hpp:103`](../src/config.hpp#L103) — `Unknown`
 - [`src/evidence_discount.hpp:2`](../src/evidence_discount.hpp#L2) — `Unknown`
 - [`src/gallery/gallery_calibration.hpp:53`](../src/gallery/gallery_calibration.hpp#L53) — `float boundary_at(float p = 0.5f, float log_prior_odds = 0.f) const`
 - [`src/main.cpp:199`](../src/main.cpp#L199) — `reg_cfg, EvidenceDiscounter(same_person));`
 - [`src/nodes/face_tracker_node.hpp:2`](../src/nodes/face_tracker_node.hpp#L2) — `Unknown`
-- [`src/nodes/identity_matcher_node.hpp:110`](../src/nodes/identity_matcher_node.hpp#L110) — `const GalleryCalibration& calibration() const { return cal_; }`
+- [`src/nodes/identity_matcher_node.hpp:111`](../src/nodes/identity_matcher_node.hpp#L111) — `const GalleryCalibration& calibration() const { return cal_; }`
 
 ### AR-025
 
-**Locations:** 1
+**Locations:** 3
 
 - [`src/evidence_discount.hpp:2`](../src/evidence_discount.hpp#L2) — `Unknown`
+- [`src/nodes/identity_matcher_node.hpp:119`](../src/nodes/identity_matcher_node.hpp#L119) — `const GalleryCalibration& calibration() const { return cal_; }`
+- [`src/nodes/identity_matcher_node.hpp:242`](../src/nodes/identity_matcher_node.hpp#L242) — `Unknown`
 
 ### DP-001
 
@@ -267,7 +277,7 @@ _None._
 
 **Locations:** 44
 
-- [`src/config.hpp:43`](../src/config.hpp#L43) — `Unknown`
+- [`src/config.hpp:49`](../src/config.hpp#L49) — `Unknown`
 - [`src/gallery/embedder_stamp.cpp:1`](../src/gallery/embedder_stamp.cpp#L1) — `Unknown`
 - [`src/gallery/embedder_stamp.hpp:2`](../src/gallery/embedder_stamp.hpp#L2) — `Unknown`
 - [`src/gallery/gallery_builder.cpp:45`](../src/gallery/gallery_builder.cpp#L45) — `ActorGallery build_gallery(const BuildConfig& cfg)`
@@ -318,6 +328,22 @@ _None._
 
 - [`src/nodes/result_sink_node.hpp:2`](../src/nodes/result_sink_node.hpp#L2) — `Unknown`
 
+### IR-002
+
+**Locations:** 5
+
+- [`src/config.hpp:20`](../src/config.hpp#L20) — `struct Config`
+- [`src/main.cpp:216`](../src/main.cpp#L216) — `reg_cfg, EvidenceDiscounter(same_person));`
+- [`src/nodes/result_sink_node.hpp:49`](../src/nodes/result_sink_node.hpp#L49) — `static constexpr std::string_view label() { return "result_sink"; }`
+- [`src/nodes/result_sink_node.hpp:122`](../src/nodes/result_sink_node.hpp#L122) — `void write_output()`
+- [`src/nodes/result_sink_node.hpp:161`](../src/nodes/result_sink_node.hpp#L161) — `struct ActorMeta { std::string name, imdb_id, tmdb_id, jellyfin_id; };`
+
+### IR-003
+
+**Locations:** 1
+
+- [`src/main.cpp:216`](../src/main.cpp#L216) — `reg_cfg, EvidenceDiscounter(same_person));`
+
 ### IR-004
 
 **Locations:** 16
@@ -398,7 +424,7 @@ _None._
 
 **Locations:** 46
 
-- [`src/config.hpp:43`](../src/config.hpp#L43) — `Unknown`
+- [`src/config.hpp:49`](../src/config.hpp#L49) — `Unknown`
 - [`src/gallery/embedder_stamp.cpp:1`](../src/gallery/embedder_stamp.cpp#L1) — `Unknown`
 - [`src/gallery/embedder_stamp.hpp:2`](../src/gallery/embedder_stamp.hpp#L2) — `Unknown`
 - [`src/gallery/gallery_builder.cpp:45`](../src/gallery/gallery_builder.cpp#L45) — `ActorGallery build_gallery(const BuildConfig& cfg)`
@@ -447,26 +473,35 @@ _None._
 
 ### SR-002
 
-**Locations:** 10
+**Locations:** 16
 
-- [`src/config.hpp:97`](../src/config.hpp#L97) — `Unknown`
+- [`src/config.hpp:103`](../src/config.hpp#L103) — `Unknown`
 - [`src/evidence_discount.hpp:2`](../src/evidence_discount.hpp#L2) — `Unknown`
 - [`src/face_utils.hpp:2`](../src/face_utils.hpp#L2) — `inline cv::Mat align_face(const cv::Mat& img,`
 - [`src/gallery/gallery_calibration.hpp:2`](../src/gallery/gallery_calibration.hpp#L2) — `Unknown`
 - [`src/gallery/gallery_calibration.hpp:53`](../src/gallery/gallery_calibration.hpp#L53) — `float boundary_at(float p = 0.5f, float log_prior_odds = 0.f) const`
 - [`src/main.cpp:199`](../src/main.cpp#L199) — `reg_cfg, EvidenceDiscounter(same_person));`
+- [`src/main.cpp:216`](../src/main.cpp#L216) — `reg_cfg, EvidenceDiscounter(same_person));`
 - [`src/nodes/face_detector_node.hpp:2`](../src/nodes/face_detector_node.hpp#L2) — `Unknown`
 - [`src/nodes/face_tracker_node.hpp:2`](../src/nodes/face_tracker_node.hpp#L2) — `Unknown`
-- [`src/nodes/identity_matcher_node.hpp:110`](../src/nodes/identity_matcher_node.hpp#L110) — `const GalleryCalibration& calibration() const { return cal_; }`
+- [`src/nodes/identity_matcher_node.hpp:111`](../src/nodes/identity_matcher_node.hpp#L111) — `const GalleryCalibration& calibration() const { return cal_; }`
+- [`src/nodes/identity_matcher_node.hpp:119`](../src/nodes/identity_matcher_node.hpp#L119) — `const GalleryCalibration& calibration() const { return cal_; }`
+- [`src/nodes/identity_matcher_node.hpp:242`](../src/nodes/identity_matcher_node.hpp#L242) — `Unknown`
+- [`src/nodes/result_sink_node.hpp:49`](../src/nodes/result_sink_node.hpp#L49) — `static constexpr std::string_view label() { return "result_sink"; }`
+- [`src/nodes/result_sink_node.hpp:63`](../src/nodes/result_sink_node.hpp#L63) — `void set_pre_write_hook(std::function<void(double)> fn) { pre_write_ = std::move(fn); }`
+- [`src/nodes/result_sink_node.hpp:161`](../src/nodes/result_sink_node.hpp#L161) — `struct ActorMeta { std::string name, imdb_id, tmdb_id, jellyfin_id; };`
 - [`src/track_registry.hpp:2`](../src/track_registry.hpp#L2) — `Unknown`
 
 ### SR-003
 
-**Locations:** 3
+**Locations:** 6
 
 - [`src/audio_signature.cpp:3`](../src/audio_signature.cpp#L3) — `Unknown`
 - [`src/audio_signature.hpp:4`](../src/audio_signature.hpp#L4) — `Unknown`
+- [`src/config.hpp:20`](../src/config.hpp#L20) — `struct Config`
 - [`src/nodes/result_sink_node.hpp:2`](../src/nodes/result_sink_node.hpp#L2) — `Unknown`
+- [`src/nodes/result_sink_node.hpp:49`](../src/nodes/result_sink_node.hpp#L49) — `static constexpr std::string_view label() { return "result_sink"; }`
+- [`src/nodes/result_sink_node.hpp:122`](../src/nodes/result_sink_node.hpp#L122) — `void write_output()`
 
 ### SR-005
 
@@ -553,3 +588,9 @@ _None._
 - `scripts/sae_gallery.py:171` — {'ignored': ['— omitted entirely when unknown', 'so "unstamped"']}
 - `scripts/sae_gallery.py:199` — {'ignored': ['— carried through so a derived gallery (filter']}
 
+**Groups mixing requirement types (pipe separates types):**
+
+- `src/main.cpp:216` — {'group': ['AR-012', 'AR-016', 'IR-002', 'IR-003']}
+- `src/nodes/result_sink_node.hpp:49` — {'group': ['AR-012', 'AR-017', 'IR-002']}
+- `src/nodes/result_sink_node.hpp:161` — {'group': ['AR-012', 'IR-002']}
+