Fix the real A/V gap: a stream copy across mixed frame rates

The rebuild after 1457556 came out byte-identical to the broken file,
which proved the xfade fix never runs for this chapter. An all-cut chapter
goes down the concat demuxer with -c copy, which writes the output in the
FIRST input's time_base and reinterprets every later packet in it. 14 of
49 clips are 30/1 at 1/15360 against 35 at 25/1 at 1/12800, so those 14
play 15360/12800 = 1.2 too long with their audio untouched. collage_cmd
hardcoded -r 30 and yesterday's FPS sweep missed it.

collage_cmd now emits -r FPS, and assemble probes r_frame_rate across the
clips and routes mixed rates through the re-encoding tree. Rebuilt
chapter.mp4 is 364.120s video against 364.122s audio at 25/1, from
436.392 over 363.675.

Also settle the bbox coordinate space, measured over all 113 detections:
47 boxes have x2 past the 900px panel width, none has y2 past 1000 on
panels up to 2307px tall, and the range is exactly [0, 1000]. It is
gemma's normalized grid, not pixels, whatever the prompt asks for.
/vision converts before returning, which fixes identity's crop, the gated
face pairing that was comparing pixel face boxes against grid boxes, the
set-of-mark boxes and the review UI at once. Checked by eye on panel 7:
five of six boxes now land on their subject, including the foreground
character who had no identity.

The registry still holds boxes and embeddings enrolled from the wrong
space. vision and identity have to re-run, which is GPU work and was not
started.

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

caveats/CLAUDE.md

@@ -38,7 +38,7 @@ a complaint, so give it one or drop it.
 | [One invented word still halts the chapter](speaker-attribution.md#one-word-halts-chapter) | 2026-08-11 run |
 | [A completed job keeps the error from an earlier failure](audit-open.md#stale-job-error) | 2026-08-11 run |
 | [`layers` reports success on an empty bucket](audit-open.md#layers-writes-nothing) | 2026-08-11 run |
-| [Every `bbox` is read in the wrong coordinate space](speaker-attribution.md#bbox-wrong-space) | 2026-08-12 panel 7 |
+| [Every `bbox` is read in the wrong coordinate space](speaker-attribution.md#bbox-wrong-space) | resolved, rerun pending |
 | [Identity cannot say "a person with no name"](speaker-attribution.md#no-anonymous-identity) | 2026-08-12 panel 7 |
 | [Vision does not separate a background extra from cast](speaker-attribution.md#extras-as-cast) | 2026-08-12 panel 7 |
 | [Cast reference profiles are enrolled from wrong crops](speaker-attribution.md#poisoned-reference-set) | 2026-08-12 panel 7 |

caveats/speaker-attribution.md

@@ -72,6 +72,13 @@ is to flag the beat for review and continue, which is `#136` gate work, not a ve
 
 ## Every `bbox` is read in the wrong coordinate space {#bbox-wrong-space}
 
+**Resolved 2026-08-12, `decisions/identity-bbox.md#bbox-is-normalized`.** The space is gemma's 0-1000
+grid, proven over all 113 detections, and `/vision` now converts to pixels before returning. The face
+pairing at `worker_vision.py:57` was reading the same numbers against real pixel face boxes, so it is
+fixed by the same change. What is left of this entry is the consequence. Every stored assignment,
+embedding and `ref_image_uris` came from a wrong crop. Identity has to re-run before any of it means
+anything. The rest below is kept as the record of how it read before.
+
 Vision's `bbox` values are stored and consumed as absolute pixels. On panel
 `7c944dd4-e972-42c7-ba60-9f6939548e80_p007` (crop 900x1650) all six boxes then land in the top third of
 the panel, two of them inside the "YEAH!" speech balloon. Divided by 1000 against the panel's own