feat(models): add refresh-model-catalog skill

Add an agent skill that walks through a full model catalog refresh: drift
detection, catalog sync, manually reviewed pricing updates, fixture
refresh, and test updates. Its helper scripts run on Windows and Linux:
one snapshots the live model-id list into the test fixture, the other
regenerates the pricing fixture from MODEL_COSTS through prettier so
format:check stays green. Typecheck now covers the skill scripts.

tsconfig.json

@@ -9,5 +9,5 @@
     "strict": true,
     "types": ["node"]
   },
-  "include": [".github/scripts/**/*.ts", "src/**/*.ts", "tests/**/*.ts"]
+  "include": [".github/scripts/**/*.ts", ".agents/skills/**/*.ts", "src/**/*.ts", "tests/**/*.ts"]
 }