feat: add Dia text animation

[starc007]

What changed

• adds Dia Text Animation as the first example in the Text Animation collection
• keeps the sentence prefix fixed while the final word cycles through a colorful reveal
• reserves the widest word with CSS Grid to prevent layout shift
• includes reduced-motion behavior, accessibility coverage, registry metadata, and a dedicated preview
• publishes the implementation through @beui/chromatic-text-reveal

Why

This gives beUI a polished, Dia-inspired headline treatment for product messaging while keeping the implementation and public API native to the library.

Validation

• bun run check
• bun test — 41 passing
• git diff --check

Biome reports one existing unrelated warning for the unused Star import in components/app/chrome/site-header.tsx.