Add AI agent guide, AGENTS.md and useWhen to component catalog

Add static demo section sync check ...

scripts/check-demo-sections.mjs verifies without a server that
demo/index.html and demo/vue.html include the identical section
sequence, that every included partial exists in both variants, and
that no partial is orphaned. Wired into release:check as
test:demo-sections.

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

Prepare package release flow

Add Vue package smoke test