feat: add bounce sidebar and improve animated component SEO

[starc007]

Summary

• add the Bounce Sidebar component, preview, registry metadata, accessibility coverage, and focused behavior tests
• smooth long-distance indicator jumps while preserving the same curved motion in both directions
• strengthen the animated React component catalog title, heading, descriptions, and internal linking
• align the homepage hero, SEO metadata, structured data, social cards, registry copy, and supporting brand surfaces around “Animated components for React and Next.js”

Why

The library needed a reusable curved-dot sidebar interaction, including smooth movement when users skip across several destinations. The site also used the less explicit “motion toolkit” positioning across search and social surfaces, making its animated React component offering harder to understand at a glance.

Impact

Users get a copy-paste Bounce Sidebar with controlled and uncontrolled modes, link or button destinations, disabled states, and reduced-motion support. Search engines, social previews, registry consumers, and visitors now receive consistent category-focused positioning.

Validation

• bun run check
• bun test tests/bounce-sidebar.test.tsx tests/a11y.test.tsx
• MCP package bun run typecheck
• 26 focused tests passed
• registry validation passed for 53 components

Biome reports one pre-existing unused Star import warning in components/app/chrome/site-header.tsx; no lint errors were introduced.