Add HyperFrames skills

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011h6NB8JQtfPc6eRCefEzBB

.agents/skills/hyperframes-animation/transitions/css-3d.md

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+## 3D
+
+### 3D Card Flip
+
+180° Y-axis rotation. Requires CSS: `backface-visibility: hidden; transform-style: preserve-3d;` on both scene-inners. Parent needs `perspective: 1200px`.
+
+```js
+tl.set(new, { rotationY: -180, opacity: 1 }, T);
+tl.to(old, { rotationY: 180, duration: 0.6, ease: "power2.inOut" }, T);
+tl.to(new, { rotationY: 0, duration: 0.6, ease: "power2.inOut" }, T);
+tl.set(old, { opacity: 0 }, T + 0.6);
+```