docs: land the registers for schema v2 and the audio signature

Status and verification rows for the six requirements landed in this
branch, plus UT-029 … UT-052, and the generated traceability matrix that
`docs/traceability.md` holds in the other two components but was missing
here. `traces-report.json` is gitignored to match the server: the matrix
is committed, the JSON report is not, since nothing reads it back.

Two corrections rather than additions:

`AudioSignatureTests` was tagged UT-029 … UT-035, IDs the register had
already assigned to the schema tests. Renumbered to UT-038 … UT-044,
matching the register, which was right — duplicate IDs defeat the point
of IDs being permanent.

`ReadCappedAsync` implements JR-028's response cap and carried no tag,
so the requirement read as uncovered.

The gate reports 0 orphan tags.

TRACES: JR-002, JR-003, JR-028, JR-041, JR-042, JR-043, JR-044, JR-045 | SR-003

SPEC.md

@@ -55,9 +55,14 @@ The truth file is **not** the Jmanifest. It carries installation-local fields
 identity block the exchange adds. See §6.
 
 **Current:** [`Models/TruthFile.cs`](Jellyfin.Plugin.JRay/Models/TruthFile.cs),
-`schema_version: 1`. **Gap:** the schema below is not implemented, and the other
-two specs describe the pending bump in more detail than this one does — the
-ownership is stated but not yet exercised.
+`schema_version: 2` — the schema below is implemented, with
+[`Models/TruthScene.cs`](Jellyfin.Plugin.JRay/Models/TruthScene.cs),
+[`Models/TruthExtraction.cs`](Jellyfin.Plugin.JRay/Models/TruthExtraction.cs) and
+[`Models/TruthCut.cs`](Jellyfin.Plugin.JRay/Models/TruthCut.cs).
+
+**Gap:** the ownership claim is still not *enforced* — nothing checks that the
+other two repos reference this section rather than restating the schema. JR-001's
+verification tier is `static` for that reason, and no such check exists yet.
 
 ### JR-002 — `schema_version: 2`
 
@@ -118,9 +123,12 @@ same upload must agree on its `content_id`, and belief is a producer-side
 estimate that may legitimately differ between pipeline versions for identical
 timings. It replicates the way `audio_signature` does — see the server spec §9a.
 
-**Gap:** entire requirement. The changes are all breaking and ship as **one**
-bump (SR-003), together with extraction `IR-002` and the server's acceptance of
-the new shape.
+**Current:** implemented. `scenes` are `TruthScene` objects carrying `belief` and
+`route`; `extraction.*` and `cut.*` are their own types; `anneal_sec` and the
+top-level `sample_fps` are **deleted, not zeroed**. `ManifestConverter` carries
+belief, route and both blocks through from a fetched manifest rather than
+flattening them. **Gap:** none — this shipped with extraction `IR-002` and the
+server's `jmanifest_version: 2` as the one coordinated SR-003 bump.
 
 ### JR-003 — Unknown `schema_version` is refused, never guessed
 
@@ -140,9 +148,20 @@ version found, rather than silently reporting no coverage — an item that looks
 un-extracted when it was merely stale is the failure mode that wastes a user's
 compute.
 
-**Current:** `PUT` rejects `schema_version != 1` with `400`; sidecar reads do not
-check the version at all. **Gap:** the version check must move into the shared
-read path so all three sources are covered, and the target becomes `2`.
+**Current:** implemented.
+[`Services/TruthSchema.cs`](Jellyfin.Plugin.JRay/Services/TruthSchema.cs) holds
+the single `SupportedVersion = 2` and is consulted on **all four** paths — sidecar
+read, managed store load, managed `PUT`, and the converter that writes a fetched
+manifest. Rejections name the file and the version found, per the paragraph above.
+
+Managed truth is checked on load as well as on `PUT`, because data written by an
+earlier plugin build is already on disk and never passed today's `PUT`.
+
+One consequence is worth stating: a v1 file usually fails to *deserialise* before
+its version can be read, since `scenes` was a float pair and is now an object. So
+both the parse-failure path and the version-gate path must name the file — a
+rejection the user cannot attribute to a stale sidecar is the failure mode JR-003
+exists to prevent. **Gap:** none.
 
 ### JR-004 — A window is a scene-membership claim
 
@@ -765,8 +784,42 @@ frames whose peak bin matches — is a **consumer** concern and belongs to this
 plugin. Offsets are applied client-side per JR-030; manifests are never
 rewritten.
 
-**Current:** `ComputeAudioSignatures` exists as a configuration switch. **Gap:**
-entire requirement, both computation and matching.
+**Current:** JR-042 and JR-043 hold. `AudioSignature` implements the construction
+above — band table, periodic Hann, radix-2 FFT, band-mean peak, energy class,
+packing — and `AudioSignatureService` decodes the centre window by running the
+FFmpeg binary `IMediaEncoder.EncoderPath` names, so the plugin gained no
+dependency. `fixtures/audio/` holds the extraction repo's three golden-vector
+files byte-identically, and the computed signature equals the recorded vector
+exactly (UT-038 … UT-044). The binding check regenerates the fixture PCM from
+`make_fixture.py`'s arithmetic and verifies it against the recorded decode
+checksums, so it runs on a CI host with no codec at all; the two tests that
+exercise the real FFmpeg decode self-skip without a binary.
+
+JR-044 and JR-045 hold as well, both halves. `AudioSignatureMatcher` is the
+reader they were waiting on: it implements the ±600-frame slide above, scoring
+the fraction of overlapping frames whose peak band agrees, and returns the tier
+and the offset. `TryParseFrames` refuses any prefix but `v1:`, so a future
+producer's `v2:` drops the item to the runtime tier rather than being scored as
+if it were understood; and a runtime under 120 s yields no match and therefore no
+offset, read off the runtime rather than inferred from a missing string, because
+the runtime is what both producers test (UT-045 … UT-052).
+
+The offset has **two terms**, which is easy to miss: the recovered slide, and the
+difference between where the two windows are anchored. Both windows are centred
+on their own file's midpoint, so unequal runtimes start them at different
+absolute times. A release carrying 40 s of extra head material recovers 20 s from
+each term.
+
+One parameter is **not** from the specification: an alignment must overlap by at
+least 64 frames (~6 s) before its score counts. Without a floor the extreme
+offsets compare a handful of frames, where a chance agreement scores 1.0 and
+beats the true alignment. It never binds on the real case — two full-length
+signatures still overlap by 688 frames at the widest offset.
+
+**Gap:** the signature is computed and can now be read, but nothing yet *calls*
+either: `ComputeAudioSignatures` still gates nothing, no fetch path attaches a
+signature or consults the matcher, and no contribution carries one. That wiring
+belongs to the fetch and contribute paths (JR-031, JR-034), not here.
 
 ---