/**
 * The worker stamps a heartbeat file from a steady timer. The stamp proves only
 * that the event loop is turning — it is INTENTIONALLY independent of command
 * workload, so a long or quiet command never looks "stuck". The supervisor reads
 * this file and force-restarts the worker only when the stamp goes stale, which
 * means a genuinely wedged loop (no benign explanation) → zero false positives.
 */
/** Default heartbeat path. Prefers the systemd RuntimeDirectory (tmpfs). */
export declare function defaultHeartbeatPath(configDir?: string): string;
/** Begin stamping `file` every `intervalMs`. Idempotent. */
export declare function startHeartbeat(file: string, intervalMs?: number): void;
export declare function stopHeartbeat(): void;
/** Read the last heartbeat epoch-ms, or null if missing/unreadable. */
export declare function readHeartbeat(file: string): number | null;