/**
 * Watches the project directory for external file changes (using built-in
 * `fs.watch` with recursive mode — supported on macOS/Windows). Fires only
 * when the agent is idle (not running) so the agent's own writes don't
 * trigger false notifications. Debounced (fs.watch fires multiple events).
 */
export declare function useFileWatcher(idle: boolean): {
    changedFile: string | null;
    clear: () => void;
};