/**
 * Execute `fn` while holding an exclusive lock on `filePath`.
 * Concurrent calls for the same path are serialized; different paths run in parallel.
 */
export declare function withFileLock<T>(filePath: string, fn: () => Promise<T>): Promise<T>;
/**
 * Number of active file locks. Useful for testing / diagnostics.
 */
export declare function activeLockCount(): number;
/**
 * Clear all locks. Only for use in tests.
 */
export declare function clearAllLocks(): void;
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