initial: mirror of @fn_library from fn_registry

75 components + DESIGN_SYSTEM.md + sync script.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

components/use_animated_canvas.md

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+---
+name: use_animated_canvas
+kind: component
+lang: ts
+domain: ui
+version: "1.0.0"
+purity: impure
+signature: "useAnimatedCanvas(options: AnimatedCanvasOptions): AnimatedCanvasResult"
+description: "Hook React para canvas animado a N fps via requestAnimationFrame. Maneja DPR, resize, throttling, y contador de FPS real."
+tags: [canvas, animation, fps, requestAnimationFrame, hook, realtime, component, ui]
+uses_functions: []
+uses_types: []
+returns: []
+returns_optional: false
+error_type: ""
+imports: [react]
+params:
+  - name: options
+    desc: "Configuración: fps (target), draw (callback de renderizado), opcionalmente DPR"
+output: "Hook que retorna canvasRef y renderFpsRef para renderizado animado a N fps"
+tested: false
+tests: []
+test_file_path: ""
+file_path: "frontend/functions/ui/use_animated_canvas.tsx"
+props:
+  - name: fps
+    type: "number"
+    required: false
+    description: "Target FPS (default 60)"
+  - name: draw
+    type: "(ctx: CanvasRenderingContext2D, width: number, height: number, frameCount: number) => void"
+    required: true
+    description: "Callback de renderizado"
+emits: []
+has_state: true
+framework: react
+variant: [default]
+---
+
+## Ejemplo
+
+```tsx
+const { canvasRef, renderFpsRef } = useAnimatedCanvas({
+  fps: 100,
+  draw: (ctx, w, h) => {
+    // Dibujar lo que sea a 100fps
+    ctx.fillStyle = '#3b82f6'
+    ctx.fillRect(0, 0, w * Math.random(), h)
+  },
+})
+
+return <canvas ref={canvasRef} style={{ width: '100%', height: 300 }} />
+```
+
+## Notas
+
+- DPR automático: escala el canvas al devicePixelRatio de la pantalla
+- Resize automático: detecta cambios de tamaño via getBoundingClientRect
+- Throttle configurable: rAF corre a ~144fps nativo, el hook filtra a N fps
+- FPS real: `renderFpsRef.current` tiene los FPS medidos (no el target)
+- drawRef pattern: actualiza el callback sin re-crear el loop de animación