/**
 * Cross-platform PID liveness check using only stdlib.
 *
 * `process.kill(pid, 0)` sends signal 0, which performs error checking
 * without actually delivering a signal:
 *   - returns successfully when the process exists and we have permission
 *   - throws EPERM when the process exists but is owned by another user
 *     (common on Windows where signals don't translate cleanly)
 *   - throws ESRCH when the process does not exist
 */
export declare function isPidAlive(pid: number): boolean;