docs: rep4 bake-off write-up, MkDocs site, artifact-registry-backed experiments

docs/rep4-optimizer-results.md is the main deliverable: the model bake-off +
threshold re-tune experiment log, including the ROCm teardown deadlock root
cause and fix, DE concurrency tuning, the 16-combo results table, held-out
validation against 5 films never seen by the optimizer (macro F1 67.4% vs.
75.3% training — a real generalization gap), the frozen-bbox "ghost track"
failure mode found via annotated frame evidence, calibration curves per model,
and an isolated-effects breakdown of gallery scope vs. pose expansion.

MkDocs site (mkdocs.yml, docs/index.md) renders docs/*.md; scripts/docs/
pulls referenced images from the artifact registry and generates the
calibration chart at build time (see the tooling commit) rather than
committing images to the repo.

experiments/ now keeps only scripts + README + SESSION_STATE.md in git — every
data artifact (galleries, dumps, X-Ray corpus, montage frames, trajectories,
manifests, results) moved to the Gitea package registry. film-lut.template.json
is the committed placeholder for the gitignored file-lut.json (real local
movie paths, never shared — some source filenames carry scene-release tags).

Adds models/transnetv2.onnx (via Git LFS, matching the other ONNX models) for
the new scene-detection path.

experiments/build_manifests.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+"""
+Build per-(model, mode) manifests for the model × gallery-mode bake-off.
+
+Modes:
+  full       — every film matches against the whole model gallery (2418 actors)
+  restricted — each film matches only its Jellyfin credited cast (~15 top-billed),
+               via a per-film gallery filtered from the model gallery by jellyfin_id.
+
+Each manifest is a list of {name, xray, slug, dump, gallery} — no "movie" path (that's
+resolved locally via experiments/file-lut.json, see run_montage_all.py, to avoid
+embedding source filenames in a file that gets shared as an artifact). optimize.py
+reads film["gallery"] per film, so restricted mode just points each film at its own
+filtered gallery — no optimizer change needed.
+
+Writes experiments/manifests/films_<model>_<mode>.json and the restricted galleries to
+experiments/galleries/restricted/<model>/<slug>.h5.
+"""
+import json
+import sys
+from pathlib import Path
+
+REPO = Path(__file__).resolve().parent.parent
+sys.path.insert(0, str(REPO / "scripts" / "validation"))
+sys.path.insert(0, str(REPO / "scripts"))
+from identity import norm_name  # noqa: E402
+from sae_gallery import load_gallery_hdf5, save_gallery_hdf5  # noqa: E402
+
+MODELS = ["arcface_w600k_r50", "arcface_r18", "arcface_w600k_mbf", "LVFace-B_Glint360K"]
+
+films = json.loads((REPO / "experiments/manifests/films.json").read_text())
+casts = json.loads((REPO / "experiments/manifests/jellyfin_casts.json").read_text())
+
+
+def restrict_gallery(model_gallery: dict, cast_ids: set[str]) -> dict:
+    kept = [a for a in model_gallery["actors"] if a.get("jellyfin_id", "") in cast_ids]
+    return {"actors": kept}
+
+
+for model in MODELS:
+    gpath = REPO / f"experiments/galleries/gallery_{model}.h5"
+    if not gpath.exists():
+        print(f"skip {model}: gallery not built yet ({gpath})")
+        continue
+    model_gal = load_gallery_hdf5(gpath)
+
+    # full mode
+    full = [{**f, "dump": f"experiments/dumps/{model}/dump_{f['slug']}.h5",
+             "gallery": f"experiments/galleries/gallery_{model}.h5"} for f in films]
+    (REPO / f"experiments/manifests/films_{model}_full.json").write_text(json.dumps(full, indent=2, ensure_ascii=False))
+
+    # restricted mode — per-film filtered gallery
+    rdir = REPO / f"experiments/galleries/restricted/{model}"
+    rdir.mkdir(parents=True, exist_ok=True)
+    restr = []
+    for f in films:
+        cast_ids = set(casts.get(f["name"], []))
+        rg = restrict_gallery(model_gal, cast_ids)
+        rgpath = rdir / f"{f['slug']}.h5"
+        save_gallery_hdf5(rg, rgpath)
+        restr.append({**f, "dump": f"experiments/dumps/{model}/dump_{f['slug']}.h5",
+                      "gallery": str(rgpath.relative_to(REPO)),
+                      "_cast_size": len(rg["actors"])})
+    (REPO / f"experiments/manifests/films_{model}_restricted.json").write_text(json.dumps(restr, indent=2, ensure_ascii=False))
+    avg = sum(r["_cast_size"] for r in restr) / len(restr)
+    print(f"{model}: full (2418) + restricted (avg {avg:.0f} actors/film) manifests written")