⚡ Bolt: Optimize timestamp lookup with binary search

[benpiper]

• 💡 What: Replaced O(N) linear search with O(log N) binary search for timestamp lookup in video playback.
• 🎯 Why: <video onTimeUpdate> fires at high frequency. Linear search over a large array of segments on every frame update causes unnecessary CPU overhead and can cause jank on the main thread.
• 📊 Impact: Reduces lookup complexity from O(N) to O(log N), eliminating lookup time overhead even for long videos with thousands of segments.
• 🔬 Measurement: Observe CPU usage during video playback in the browser profiler. The handleTimeUpdate execution time should be measurably reduced.

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PR created automatically by Jules for task 8043746727099159522 started by @benpiper

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