feat: add live demos to vbi-react docs

[LoganLCX]

Summary

• add generated live demos for @visactor/vbi-react component API pages and switch component API outputs to MDX
• expose focused starter-based demo components and group the vbi-react examples around hooks, components, and full-page usage
• fix the embedded starter demo styling by importing starter tokens/styles locally and loosen PracticePreview typing so the docs site can render the practice previews

Validation

• pnpm --filter @visactor/vbi-react run build:api
• pnpm --filter @visactor/vbi-react run build:examples
• pnpm --filter vbi-react-starter run build
• pnpm --filter website run typecheck
• git push pre-push hook: turbo typecheck