docs: richer report — data figures, success/failure frames, commit-pinned repo links

- experiment_charts.py generates 4 figures from experiments/ artifacts:
  held-out per-film F1, 16-combo ranking, DE search landscape, and the
  Downton detector-vs-tracker ghost timeline (replaces the blank
  title-card screenshot)
- new frames: 19-correct wedding shot (success case), Many Saints
  ghost-vs-unknown frame (three error classes in one image)
- rename rep4-optimizer-results.md -> model-bakeoff.md; rep4 kept only
  as the on-disk artifact prefix, explained once
- repo file references are now links via https://REPOLINK/<path>
  placeholders; build_site.sh pins them to the HEAD commit's raw URLs
  and fails the build if a linked path doesn't exist at HEAD
- drop references to removed scripts (scene_score.py, score_config.py)
  and to session-memory names; mark artifact-registry paths with their
  pull commands
- commit readme_example.jpg + pipeline_topology.svg so README renders
  on the plain Gitea repo view
- deploy_pages.sh: push built site/ to the gitea-pages branch

mkdocs.yml

@@ -23,7 +23,7 @@ nav:
     - Gallery Scope (Full vs. Limited): gallery-scope.md
     - Pose Expansion: pose-expansion.md
     - LVFace Deep Dive: lvface-deep-dive.md
-  - Rep4 Bake-off & Re-tune (full log): rep4-optimizer-results.md
+  - Model Bake-off & Re-tune (full log): model-bakeoff.md
   - Optimizer Experiments (prior round): optimizer-experiments.md
   - Service Conversion (proposal): service-conversion.md