⚡ Bolt: [performance improvement] Replace .map().join with standard for loops in search render

[ImChong]

💡 What: Replaced .map().join('') with a standard for loop string concatenation in frontend search UI rendering (buildResultCardHtml and renderCards inside docs/main.js).
🎯 Why: Chaining .map() and .join('') allocates intermediate arrays and function closures on every loop iteration, which causes excessive memory overhead and GC pressure in hot execution paths like result rendering.
📊 Impact: Eliminates unneeded allocations for every rendered search card tag and overall result list, significantly lowering memory pressure and reducing UI latency during typing.
🔬 Measurement: Verify by searching keywords (e.g. "control") on the frontend, rendering results should be fast and visual functionality correctly preserved.

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PR created automatically by Jules for task 8511444457533556999 started by @ImChong

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