⚡ Bolt: [performance improvement] Optimize FileList selection lookups

[TheerasakPing]

💡 What:

Replaced Array.prototype.some() lookups for selectedItems and clipboard.items inside the sortedItems.map loop with Set.prototype.has() lookups. The Sets are derived outside the render loop using useMemo.

🎯 Why:

The previous implementation checked every file against the array of selected items and cut items using .some(). This creates an O(N*M) time complexity during every render (where N is the number of files and M is the number of selected/cut items). For a large directory with many selected files, this causes severe layout thrashing and freezes the UI.

📊 Impact:

Reduces the render complexity of FileList.jsx from O(N*M) to O(N+M). Lookups inside the map are now O(1). This should significantly improve responsiveness when selecting multiple files in large directories.

🔬 Measurement:

1. Open a directory with 10,000+ files.
2. Select 1,000+ files (e.g., via Shift+Click).
3. Observe the time taken to render the selection. The UI should remain responsive and not freeze.
4. Try cutting the selected files (Ctrl+X). The UI should quickly apply the 'cut' visual styling.

📝 Journal Entry

Added a journal entry to .jules/bolt.md documenting this hidden O(N*M) complexity anti-pattern in React list rendering.

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PR created automatically by Jules for task 8749685279662609049 started by @TheerasakPing

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