fix: Prevent input content reset in Breadboard editor

[yoichiro]

Summary

• Fix input content reset issue in Breadboard editor component
• Add useRef to track current file ID for proper state management
• Prevent unnecessary local state updates during Redux state synchronization

Problem

Users experienced input content disappearing while typing in the Breadboard editor. This occurred due to:

1. Local state being reset when Redux state updated
2. Timing conflicts between user input and debounced save operations
3. Monaco Editor's controlled component behavior causing content loss

Solution

• Added currentFileRef to track the currently selected file ID
• Modified useEffect to only update local state when a different file is selected
• Preserved user input during same-file editing sessions
• Maintained existing debounced save functionality

Test plan

• Verify typing in editor no longer causes content to disappear
• Confirm file switching still works correctly
• Test debounced save functionality remains intact
• Check multiple rapid file switches work properly

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