v0.3.0 — GnUserCard, NavigationShell footer slot, Vue demo partials ...

Features:
- Add GnUserCard Vue component with compact and full variants
- Add GnNavigationShell #footer slot for custom footer content
- Add profile footer demo in navigation-shell section
- Split demo/vue.html into 27 partials under demo/partials/vue/
- Fix toast open animation (nextTick + requestAnimationFrame pattern)

Style:
- Add .user-card and .user-card-compact to _cards.scss
- Add .profile-identity to _navigation-shell.scss

Docs:
- Add demo synchronization rules to CLAUDE.md

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>