feat: add configurable file watcher performance settings for multi-worktree optimization

[roomote]

This PR attempts to address Issue #8131, specifically the question about CPU optimization for multi-worktree use cases.

Summary

Adds two new configurable settings for file watcher performance optimization:

• codebaseIndexFileWatcherDebounceMs: Debounce delay for batching file changes (100-5000ms, default 500ms). Higher values batch more file changes together, reducing CPU spikes.
• codebaseIndexFileWatcherConcurrency: Concurrency limit for file processing (1-20, default 10). Lower values process fewer files in parallel, reducing peak CPU usage.

These settings help reduce CPU usage when running multiple worktrees simultaneously by allowing users to:

1. Increase debounce delays to batch more changes together
2. Reduce concurrency limits to lower peak CPU usage

Changes

• Add new constants and defaults in constants/index.ts
• Add new fields to codebase-index types schema
• Update CodeIndexConfigManager to load and expose the new settings
• Update FileWatcher to use configurable debounce and concurrency values
• Update service-factory to pass settings from config manager to file watcher
• Add comprehensive tests for all new functionality

Testing

• All existing tests pass
• Added new tests for configurable performance settings in both config-manager.spec.ts and file-watcher.spec.ts
• TypeScript type checking passes

Related Issue

Addresses #8131 - Per-workspace control for Codebase Indexing (reduce GPU)

Feedback and guidance are welcome!

[roomote]

Rooviewer   See task on Roo Cloud

Review completed. No issues were found in this PR.

The implementation is well-structured and follows existing codebase patterns:

• Schema validation with proper min/max bounds
• Constants properly centralized in packages/types
• Config manager correctly loads settings with fallback to defaults
• File watcher uses configurable debounce and concurrency values
• Comprehensive test coverage for new functionality

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}