⚡ Bolt: Remove DOM query from animation loop in HyperScrollIntro

[kaitoartz]

💡 What: Removed item.el.querySelector('.intro-card') from the requestAnimationFrame loop in HyperScrollIntro and replaced it with a cached item.cardEl reference set during initialization.

🎯 Why: Querying the DOM inside an animation loop forces the browser to evaluate the DOM tree structure up to 60 times per second per element, severely degrading frame rates on lower-end devices by blocking the main thread.

📊 Impact: Eliminates repeated O(N) DOM node lookups inside a hot path, making the update operation O(1) and significantly lowering CPU overhead during the intro animation.

🔬 Measurement: Verify by profiling the CPU main thread during the scroll intro on a simulated "low-tier" mobile connection/device—the time spent in requestAnimationFrame handler should be noticeably reduced.

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PR created automatically by Jules for task 3337083058878210582 started by @kaitoartz

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