tools: add screenshot judge script using OpenRouter vision

- Tools/judge_screenshot.py: judges a screenshot against an expected-scene
  description via OpenRouter multimodal image understanding, reading
  OPENROUTER_API_KEY from the ignored .env. --image+--expect for one shot,
  --shots to run every review shot in Screenshots/README.md. Returns a
  {verdict, confidence, reason, missing} JSON.
- Documented in AGENTS.md (Visual review pre-check step) and Tools/README.md;
  recorded the OpenRouter payload format gotcha in MEMORY.md.

AGENTS.md

@@ -99,9 +99,10 @@ Always use a consistent scale test, named export presets, and repeatable import
 Any change that affects the game's appearance — meshes, materials, lighting, levels, character, camera, post-processing — must be rendered for human review:
 
 1. Run `Tools/render_screenshots.sh` (rebuilds `Game/GigLine/Content/Test/ReviewMap.umap` from current content, runs the game on it, captures the fixed camera list, copies the PNGs into `Screenshots/`).
-2. Update `Screenshots/README.md`: one row per screenshot with what it shows and an approval state; describe any new shots or scene changes in the same change.
-3. The PNGs **are committed** so reviewers see exactly what the build rendered (`.gitignore` does not exclude them). Keep them in sync with this README: drop retired shots in the same change.
-4. Wait for the user's approval before treating a visual change as done; record approval by ticking the table in `Screenshots/README.md`.
+2. Optional pre-check with a vision model: `Tools/judge_screenshot.py --image <shot.png> --expect "<what it should show>"` (or `--shots` to run every shot in the README) flags likely-missing content before a human looks. It reads `OPENROUTER_API_KEY` from `.env` (ignored). Small helper only — it never replaces the human verdict.
+3. Update `Screenshots/README.md`: one row per screenshot with what it shows and an approval state; describe any new shots or scene changes in the same change.
+4. The PNGs **are committed** so reviewers see exactly what the build rendered (`.gitignore` does not exclude them). Keep them in sync with this README: drop retired shots in the same change.
+5. Wait for the user's approval before treating a visual change as done; record approval by ticking the table in `Screenshots/README.md`.
 
 New content that needs a different camera angle gets a new entry in the shot list in `Tools/ue_build_review_map.py`.