Make the vision judge discover cost-effective OpenRouter models

Add openrouter_judge.py to rank live image+JSON models by advertised price,
with ordered fallbacks, auth-error handling and auto selection. Wire both judges
to --model auto, record the model used, and add fake-catalogue/mocked-call
tests. Re-run the judges with the valid key: 13/13 screen designs match, 0 diff;
the Forward+ A/B report records the selected model and ~$0.006 spend. Headless
231/231, Python 94/94.

docs/asset-tooling.md

@@ -185,6 +185,12 @@ python3 tools/scene_concepts.py realism --run docs/screens/realism/<run> --judge
   --model google/gemini-2.5-flash --repeats 3
 ```
 
+Judges default to `--model auto`: `tools/openrouter_judge.py` reads the live
+OpenRouter catalogue, keeps image-input models that support `response_format`,
+and ranks them by advertised token/image price. The run falls through the list
+on provider/model errors and aborts on an invalid key. Use
+`GIG_LINE_JUDGE_MODEL` or `--model <id>` for a pinned comparison.
+
 `capture_realism.gd` runs six stages (day, portrait, evening, late, Joke Shop, studio);
 `--stages=day,late` limits it while tuning; `--flashlight` turns on the guard lamp for
 night stages (used by the Desktop HQ A/B). The `portrait` shot freezes one NPC on open sidewalk