Add compact .btn-icon-sm and fix copy-button demo ...

- Introduce `.btn-icon-sm` (28×28, 18 px icon) in `_buttons.scss` for
  a miniature icon-button variant.
- Remove `.btn-secondary` from demo copy buttons so they render as
  transparent icon-only controls without background.
- Add `size` prop to `GnIconButton` and `GnCopyButton` Vue components.
- Update docs and demo to reflect the new size option.

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

Improve Vue adapter usability, add router support, and fix animations ...

- Remove hover rotation from .btn-icon (SCSS)
- Fix iconNode to auto-prefix missing "ph-" and warn in dev
- Add CLAUDE.md as AI agent quick-reference for component usage
- Include src/vue/ and CLAUDE.md in published package files
- Add exports field wildcard for src/vue/* subpaths
- Reposition Vue adapter docs as primary contract (not thin wrapper)
- Add JSDoc @typedef to key Vue components (GnButton, GnInput, etc.)
- Add Vue demo page (demo/vue.html) linked from main navigation

Router support (optional, no hard dependency):
- Create useVueRouter composable with safe getCurrentInstance access
- Create GnRouterTabs component for route-driven tabs
- Add item.to support to GnNavList with auto-active and router.push
- Forward activeMatch through GnNavigationShell to GnNavList
- Register GnRouterTabs in plugin and index exports
- Update docs (README, CLAUDE, component-api, ai-usage-guide, component-map)

Fix missing close animations in Vue components:
- GnModal: a-hide transition before unmount (300ms)
- GnDrawer: a-hide transition before unmount (300ms)
- GnToastProvider: dismiss with a-hide animation, close for instant clear

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

Modernize Sass build pipeline

Add navigation overlays components

Scaffold GNexus UI kit