/**
 * Shared recursive project-tree watcher.
 *
 * Several subsystems each used to open their own `fs.watch(projectRoot,
 * {recursive:true})` — the codebase indexer, the chronicle file observer, and
 * the WebUI indexing mirror. Every recursive watch makes the OS track the
 * whole tree independently, so a single runtime paid that cost 2–3×. This
 * registry keeps ONE watcher per resolved root per process and fans events
 * out to all subscribers; the watcher closes when the last subscriber leaves.
 *
 * The registry lives behind a `Symbol.for` global so it stays a singleton
 * even if core is loaded twice (Windows path-casing double-load).
 *
 * @module utils/project-watch
 */
export interface ProjectWatchEvent {
    eventType: 'rename' | 'change';
    /** Path relative to the watched root as delivered by the OS, or null when omitted. */
    filename: string | null;
}
export interface ProjectWatchSubscription {
    close(): void;
}
/**
 * Subscribe to recursive change events under `root`, sharing one OS watcher
 * per root per process. Throws when the platform cannot create the watcher
 * (no recursive support, permission) and no live shared watcher exists —
 * callers that can degrade should try/catch exactly as they would `fs.watch`.
 *
 * The watcher is non-persistent: it never keeps the process alive.
 */
export declare function watchProjectTree(root: string, listener: (event: ProjectWatchEvent) => void, opts?: {
    onError?: ((error: unknown) => void) | undefined;
}): ProjectWatchSubscription;
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