Final polish, functional audit, and new Vue components ...

- Fix interactive overlay pointer-events for modal/drawer
- Add accordion panel transition so animation completes
- Fix toast inline handler syntax escaping
- Install real Phosphor Icons fonts and CSS
- Add auto-init for browser helpers and GNexusUIKit alias
- Add functional Playwright tests for all interactive components
- Add new Vue components: GnIconButton, GnInputGroup, GnDescriptionList, GnEmptyState, GnPageHeader
- Update kit.scss with new component styles
- All 17 e2e tests, Vue adapter smoke, and production build passing

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

Add overlay components: Modal, Drawer, Toast system ...

- Add SCSS for modals, drawers and toasts with VMK design tokens.
- Add GnModal and GnDrawer Vue adapters with focus trap, Escape close and teleport.
- Add browser Toasts helper and GnToastProvider + useToast composable.
- Wire overlays into plugin, Vue entry and browser bundle.
- Add demo partials for Modal, Drawer and Toast.
- Update component coverage and project notes.