refactor(bench): SuperHero replaces Road to Bali as the reference film

Bali was chosen because the TRECVID DVU set ships character mugshots, but
its reference crops are unusable at scale: median detected face 27 px
against a 69 px maximum, so every reference was upscaled 4x or more past
what the embedder was trained for (AR-011). A 66 px floor left 2 of 69
references; no threshold exists that both keeps the faces in distribution
and leaves enough of them to calibrate.

SuperHero is 69 px median and 241 px max. Its gallery builds at a 66 px
floor with 14 references over 5 characters, and calibrates on its own
(a=15.2867 b=-4.98633, 100% train accuracy) instead of borrowing constants.

Measured on the fused 17-minute film, one stream rather than per-scene
clips so presence windows cross real scene boundaries as SR-002 intends:
precision 1.00, recall 0.65, F1 0.79 — 13 true positives, 0 false
positives, 7 misses. Every out-of-gallery character was declined rather
than forced onto a nearest match. The misses are the short scenes (14 s,
38 s, 27 s), consistent with per-track accumulation needing sightings.

- build_gallery gains --min-face-px, filtering the *detected face* rather
  than the crop. The DVU images are scene crops, not mugshots, so crop
  dimensions say nothing about face scale. A poisoned reference is
  permanent in a way a bad frame is not: it corrupts every future match
  against that identity.
- scripts/fetch_dvu.sh fetches mugshots, scene graphs and segmentation for
  any DVU film. NIST names the same film three different ways, so KG_DIR
  and KG_FILE are overridable rather than derived. This exists as a script
  because the first copy of this data was assembled ad hoc in /tmp and was
  lost with it, taking the working gallery along.
- Replay fixtures move to the artifact registry: push/pull_artifacts.sh
  gain a replay-fixtures target, and tests/fixtures/dumps/.gitignore keeps
  them out of git. superhero.h5 is ~9 MB and regenerating it needs the
  film, the models and a GPU — none of which CI has. The gallery ships
  with the dumps, since a dump only replays against the gallery it was
  produced with.
- AR-012 and AR-013 coverage is ported onto the new fixture rather than
  dropped with the Bali cases: 12369 assertions, up from 7991, since the
  film is an order of magnitude larger than the clips.

Suite: 15679 assertions, 101 test cases.

TRACES: AR-011, AR-012, AR-013 | VR-001, VR-005 | SR-002

tests/fixtures/audio/make_offset_fixture.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 #
-# Regenerate bali_offset_200s.flac — the real-audio fixture behind VR-014, the
+# Regenerate superhero_offset_200s.flac — the real-audio fixture behind VR-014, the
 # audio-signature offset-recovery validation.
 #
 #     sh make_offset_fixture.sh /path/to/clips
@@ -12,8 +12,8 @@
 # one signature against another finds the true alignment and only the true
 # alignment. Tones are pathologically easy for that; dialogue and score are not.
 #
-# Source: five scene clips from "Road to Bali" (1952), the public-domain corpus
-# this repo already uses for the replay fixtures — tests/fixtures/dumps/bali_*.h5
+# Source: scene clips from SuperHero (TRECVID DVU development set), the corpus
+# this repo already uses for the replay fixtures — tests/fixtures/dumps/superhero.h5
 # are dumps of these same clips. Each is under the 120 s window on its own
 # (29-77 s), so they are concatenated in scene order to make a source long
 # enough that a 120 s window can slide inside it.
@@ -41,13 +41,13 @@
 
 set -eu
 
-CLIPS="${1:-../../../../bali}"
-OUT="$(dirname "$0")/bali_offset_200s.flac"
+CLIPS="${1:-../../../../hero}"
+OUT="$(dirname "$0")/superhero_offset_200s.flac"
 LIST="$(mktemp)"
 trap 'rm -f "$LIST"' EXIT
 
 for scene in 13 27 28 31 46; do
-    clip="$CLIPS/Road_To_Bali-$scene.webm"
+    clip="$CLIPS/SuperHero-$scene.webm"
     [ -f "$clip" ] || { echo "missing clip: $clip" >&2; exit 1; }
     echo "file '$(cd "$(dirname "$clip")" && pwd)/$(basename "$clip")'" >> "$LIST"
 done

tests/fixtures/dumps/.gitignore

@@ -0,0 +1,17 @@
+# Replay fixtures are distributed as artifacts, not through git.
+#
+# They are large (superhero.h5 is ~9 MB) and regenerating one needs the film,
+# the models and a GPU — none of which CI has. So they live in the Gitea
+# generic package registry and are fetched on demand:
+#
+#   scripts/artifacts/pull_artifacts.sh replay-fixtures [version]
+#   scripts/artifacts/push_artifacts.sh replay-fixtures
+#
+# The gallery ships alongside the dumps deliberately: a dump only replays
+# meaningfully against the gallery it was produced with.
+#
+# bali_*.h5 predate this and remain tracked; do not add more to git.
+superhero.h5
+hero66.h5
+gt.json
+scene_bounds.json