feat: add animated multi select

[starc007]

Summary

• add composable, searchable Multi Select primitives with controlled and uncontrolled state
• reuse the Combobox-style portalled, collision-aware morphing panel and keyboard navigation
• animate selected pill entry, removal, and shared layout movement with reduced-motion support
• add the component preview, registry metadata, launch date, and shared accessibility coverage

Validation

• bun run check
• bun test (389 passed)
• bun test tests/a11y.test.tsx (72 passed)
• git diff --check