/**
 * Log file output with rotation.
 * Appends structured JSON log lines to a file synchronously.
 * Rotates when file exceeds maxBytes, keeps up to `keep` old files.
 */
export declare function initLogFile(path: string, maxB?: number, keepCount?: number): void;
export declare function writeLogLine(line: string): void;
export declare function closeLogFile(): void;
