Generate CLAUDE.md component catalog from a single source ...

- docs/catalog.json is now the source of truth for the Component Catalog
- scripts/generate-catalog.mjs renders the table into CLAUDE.md (between
  GENERATED markers) and validates every listed prop/slot against the
  actual declarations in src/vue/components/*.js
- fixed stale catalog rows found by the validator: GnUsageMeter, GnSteps,
  GnAvatar, GnStatusCard, GnMetricCard
- test:catalog (--check) wired into release:check