feat(animated-theme-toggler): add controlled mode for next-themes

[Yeom-JinHo]

Closes #968.

Summary

AnimatedThemeToggler mutated html.dark and localStorage directly, so useTheme() from next-themes stayed stale until refresh. Adds opt-in controlled props:

theme?: "light" | "dark"
onThemeChange?: (theme: "light" | "dark") => void

• Uncontrolled (theme undefined): unchanged — no migration.
• Controlled: skips localStorage (avoids next-themes key collision), still toggles html.dark synchronously for View Transitions, calls onThemeChange so the parent syncs its context.

Chose theme/onThemeChange over the issue's onToggle callback because it matches the shadcn controlled pattern and eliminates the double localStorage write under the same "theme" key.

Usage

const { resolvedTheme, setTheme } = useTheme()

<AnimatedThemeToggler
  theme={resolvedTheme === "dark" ? "dark" : "light"}
  onThemeChange={setTheme}
/>

Changes

• animated-theme-toggler.tsx — add controlled props, branch applyTheme.
• animated-theme-toggler-next-themes-demo.tsx — new demo.
• registry-examples.ts — register demo.

Test plan

• pnpm lint passes.
• Uncontrolled demo still toggles + persists across reloads.
• New next-themes demo: sibling reading useTheme().resolvedTheme updates without refresh.
• Clip-path animation plays in Chrome and Firefox.

[vercel]

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