/**
 * Try to acquire the mention lock. Returns false when another live process
 * holds it (mention already being handled). Stale locks (older than TTL)
 * are taken over.
 */
export declare function acquireMentionLock(agentId: string, messageId: string, ttlMs?: number): boolean;
/** Release a previously acquired lock (best-effort). */
export declare function releaseMentionLock(agentId: string, messageId: string): void;