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.

mkdocs.yml

@@ -0,0 +1,42 @@
+site_name: scene-actor-extraction
+site_description: Face-recognition pipeline for finding on-screen actor presence in film/TV, built on KPN++
+repo_url: https://gitea.tourolle.paris/dtourolle/scene-actor-extraction
+repo_name: dtourolle/scene-actor-extraction
+
+theme:
+  name: material
+  palette:
+    - scheme: slate
+      primary: indigo
+      accent: indigo
+  features:
+    - navigation.tabs
+    - navigation.sections
+    - navigation.top
+    - content.code.copy
+    - content.code.annotate
+
+nav:
+  - Home: index.md
+  - Rep4 Bake-off & Re-tune: rep4-optimizer-results.md
+  - Optimizer Experiments (prior round): optimizer-experiments.md
+  - Service Conversion (proposal): service-conversion.md
+
+markdown_extensions:
+  - admonition
+  - toc:
+      permalink: true
+  - pymdownx.highlight:
+      anchor_linenums: true
+      line_spans: __span
+      pygments_lang_class: true
+  - pymdownx.inlinehilite
+  - pymdownx.superfences
+  - pymdownx.tabbed:
+      alternate_style: true
+  - pymdownx.snippets:
+      base_path: ['.']
+      check_paths: true
+  - pymdownx.details
+  - attr_list
+  - md_in_html