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.
execFile cannot spawn npm's .cmd shim directly on Windows, so the catalog
sync and drift check failed with spawn npm ENOENT. Route npm invocations
through the shell with argument quoting on Windows and keep direct
execFile calls elsewhere.
Thomas Byr