docs: VR-013 and VR-014 results; AR-002 raised to 40px

Records study results and the requirement change that follows from them.

VR-013 measures minimum face size end to end — gallery from one recording,
probes from another — rather than by degrading an already-aligned crop. Holding
90% of the plateau needs ~50 px that way against VR-005's ~22 px, the gap being
detection and landmark error rather than the embedder. AR-002 therefore takes
40 px, not 32: VR-005 isolates the embedder and is an upper bound, and 32 admits
faces in the falling region. FPI stayed 0.0% at every scale, and the ceiling is
cross-view rather than resolution.

VR-014 exercises audio-signature offset recovery on real film audio instead of
the synthetic golden tone. Forty random in-cap offsets, every one recovered to
the nearest frame, worst error 46 ms against a 500 ms budget — and 46 ms is the
quantisation floor rather than a result, since offsets land on whole 92.88 ms
frames. The runtime/2 anchor is confirmed through head-trimmed files.

The soft spot VR-014 found is tier labelling, not accuracy: the score drops with
sub-frame misalignment, so 27 of 40 correct alignments were demoted to `loose`.
One frame of slack in the score restores all forty to `audio` with false matches
unmoved.

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

TRACES: AR-002, VR-005, VR-013, VR-014 | SR-002, SR-003

docs/requirements.md

@@ -29,7 +29,7 @@ Status: `Done` · `In Progress` · `Planned` · `TBD` · `Withdrawn`
 | ID | Requirement | Traces to | Priority | Status |
 |---|---|---|---|---|
 | AR-001 | Detect faces in sampled frames; emit bbox, confidence, 5-point landmarks in original pixel space | SR-002 | High | Done |
-| AR-002 | Minimum face size **32×32 px** (VR-005 measured), expressed in **original** resolution (decoupled from `dense_scale`) | SR-002 | High | Planned |
+| AR-002 | Minimum face size **40×40 px** (VR-013 measured end to end; VR-005's 32 px is an embedder-only upper bound), expressed in **original** resolution (decoupled from `dense_scale`) | SR-002 | High | Planned |
 | AR-003 | No fixed per-frame face cap — crowd scenes must not lose background cast | SR-002 | Medium | **Done** — `max_faces` defaults to 0 (no cap); the matcher batches through its GEMM buffer instead of throwing |
 | AR-004 | Backpressure: unbounded faces/frame absorbed by slowing, never by dropping or throwing | SR-002 | High | **Done** — KPN node outputs use `push_blocking`; sentinels stay out-of-band. Verified: 385/385 frames, 0 drops, byte-identical across runs |
 | AR-005 | Align to 112×112 via ArcFace 5-point similarity transform, fitted by **Umeyama least squares over all five points** (as InsightFace does) — never a robust fit, which would discard the landmarks AR-030 reads | SR-002 | High | **Done** — `umeyama_similarity()`. The RANSAC fit it replaces disagreed by a median 17 source px on 400 headshots, 83.5% of crops embedding below cos 0.99, and was unstable and RNG-driven: rebuilding caught 1614 near-duplicates against the original build's ~100. **All galleries rebuilt** (2456 actors, 10254 embeddings); measured separation gain is small (0.583 → 0.590), so recorded accuracy figures should be re-run but are not expected to move far |
@@ -107,7 +107,7 @@ Status: `Done` · `In Progress` · `Planned` · `TBD` · `Withdrawn`
 | VR-002 | Replay drives the **real** KPN nodes, not a reimplementation | PR-002 | High | **Done** — replay driven from committed fixtures in `tests/test_replay_fixtures.cpp`; determinism asserted |
 | VR-003 | Scoring: micro-F1 against X-Ray, precision/recall logged at every evaluation | PR-002 | High | Done |
 | VR-004 | Reproducible validation corpus with ground truth | PR-002 | High | Done |
-| VR-005 | Minimum face size study — TPI/FPI vs probe size, gallery held at native res | PR-002 | Medium | **Done** — knee at 24–32 px; 32 px gives 98.1% TPI, 0.0 FPI at every size |
+| VR-005 | Minimum face size study — TPI/FPI vs probe size, gallery held at native res | PR-002 | Medium | **Done** — knee at 24–32 px; 32 px gives 98.1% TPI, 0.0 FPI at every size. Degrades an already-aligned 112×112 crop, so it isolates the embedder and is an **upper bound**; VR-013 measures the same question end to end and AR-002 takes its number, not this one |
 | VR-006 | Re-tune `scene_threshold` once native-rate decode lands | PR-002 | Low | Planned |
 | VR-007 | Expansion band, clustering threshold, and deferred-pass ablation | PR-002 | Medium | Planned |
 | VR-008 | Gallery scaling benchmark — throughput vs gallery size | PR-002 | Medium | Planned |
@@ -115,7 +115,8 @@ Status: `Done` · `In Progress` · `Planned` · `TBD` · `Withdrawn`
 | VR-010 | Dump provenance attributes — embedder model, detector settings, `dense_scale`, `scene_detect`, sample rate | PR-002 | **High** | Planned |
 | VR-011 | Rewrite the replay harness for the post-AR-012 output contract | PR-002 | High | Planned |
 | VR-012 | Quality-knee study — TPI/FPI vs sharpness and vs pose, as VR-005 did for size; also settles whether the 5-point pose proxy needs a dedicated landmark model | PR-002 | Medium | Planned |
-| VR-013 | Cross-source identification probe — gallery from one recording, probes from another, swept over input resolution end to end | PR-002 | Medium | In Progress |
+| VR-014 | Audio-signature **offset recovery on real content** — a known trim recovered from film audio, not from the synthetic golden tone | PR-002 | Medium | **Done** — 40 random in-cap offsets, every one recovered to the nearest frame: **worst error 46 ms against a 500 ms budget**, and 46 ms is the floor rather than a result, since the offset is quantised to whole 92.88 ms frames. The `runtime/2` anchor confirmed through real head-trimmed files (a `delta` trim moves the window by `delta/2`). The one soft spot is **tier labelling, not accuracy**: the score falls with sub-frame misalignment (0.94–0.99 near a frame boundary, 0.69–0.73 at half a frame), so 27/40 correct alignments were demoted to `loose`. ±1 frame of slack in the *score* fixes it — measured, all 40 back to `audio` (min 0.906), false matches unmoved at 0.12–0.16, costing 81 ms of the budget |
+| VR-013 | Cross-source identification probe — gallery from one recording, probes from another, swept over input resolution end to end | PR-002 | Medium | **In Progress** — holding 90% of the plateau needs ~50 px end to end against VR-005's ~22 px, the gap being detection and landmark error; **`min_face_px` 40, since 32 admits faces in the falling region** (AR-002). FPI 0.0% at every scale. Ceiling is cross-view, not resolution |
 
 ---
 
@@ -200,7 +201,7 @@ as such rather than counted as covered.
 | Requirement | Tier | Note |
 |---|---|---|
 | AR-001, AR-005, AR-006 | T3 | Smoke only — correctness of detection/embedding is a model property, not ours |
-| AR-002 | Minimum face size **32×32 px** (VR-005 measured), expressed in **original** resolution (decoupled from `dense_scale`) | Size filtering is arithmetic on dumped bboxes |
+| AR-002 | T2 | Size filtering is arithmetic on dumped bboxes |
 | AR-003, AR-004 | T1 + T4 | Backpressure logic is unit-testable; saturation behaviour needs real load |
 | AR-007 … AR-017 | **T2** | The core of the redesign — fully replayable |
 | AR-018 … AR-022 | **T2** | Expansion, deferred pass, clustering: all post-embedding |
@@ -241,9 +242,10 @@ 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.
+  the AR-002 minimum of 40 px (original resolution) sits at the very bottom of
+  that range: the filter is close to binding, and anything shot wider is lost.
+  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
@@ -307,7 +309,7 @@ because it will be trusted.
 | ID | Tier | Test asserts | Edge cases to cover |
 |---|---|---|---|
 | AR-001 | T3 | Detector returns plausible boxes on a known frame | — smoke only |
-| AR-002 | T2 | Faces below 32 px (original res) are dropped | Exactly at threshold; with `dense_scale` 0.5 — the interaction that motivated the requirement |
+| AR-002 | T2 | Faces below 40 px (original res) are dropped | Exactly at threshold; with `dense_scale` 0.5 — the interaction that motivated the requirement |
 | AR-003 | T2 | No cap applied; a 40-face frame yields 40 | Crowd frame |
 | AR-004 | T1 | Saturated input blocks rather than drops or throws | Bounded queue at capacity; **byte-based** limit with large crops; SIGTERM mid-block |
 | AR-005 | T1 | Known landmarks → expected 112×112 warp; the fit never mirrors | Landmarks near frame edge; degenerate/collinear points; a mirrored set — SVD returns a reflection unless the determinant guard rejects it |
@@ -340,6 +342,7 @@ because it will be trusted.
 | IR-001/002 | T1 | Serialised output matches golden file | Zero-length window; actor with many windows |
 | IR-003 | T1 | Output written after deferred pass | Not at EOF |
 | IR-004/005 | **T1** | Signature matches golden vector bit-for-bit | Identical result in both producer repos |
+| VR-014 | **T2** | A known trim offset is recovered from **real film audio**, to the nearest frame | An offset past the ±600-frame cap and unrelated content must both be *declined*, never given a best-effort alignment. Fixture and signature are both CPU-only, so unlike the other VR rows this one is CI-*executable* — though the repo's only workflow today is the traceability gate, so nothing runs it there yet. The signature comes from the shipped C++ through `sae_audio`; a numpy port would be a third implementation nobody checks against the golden vector |
 | IR-006 | T1 + manual | Queue pull and result push against a stubbed Jellyfin API | Partial result never pushed; push only after the deferred pass |
 | IR-007 | **T1** | Media < 120 s emits no signature at all | Exactly 120 s; just under; zero-length audio. Must match the plugin's cutoff exactly — a caller-varying window length is what SR-004 forbids |
 | IR-008 | T1 | `v1:` prefix emitted and honoured on read | Unknown prefix rejected, not guessed |