- Add watch() method using Node's built-in fs.watch with recursive option
- Detect task.json changes and emit appropriate SSE events (created/moved/updated/deleted)
- Debounce per-file changes (150ms) to coalesce rapid writes
- Suppress duplicate events for in-process mutations via recentlyWritten set
- Integrate watcher into dashboard server startup with clean SIGINT shutdown
- Add @types/node to core package for proper TypeScript support
