/**
 * 零依赖 JSONL exporter — 每次 export 追加一行 JSON。
 *
 * - `createWriteStream({flags: "a"})` append 模式
 * - 循环引用 / 非法值转 `String(err)`，不抛
 * - `close()` 幂等；close 后 `export()` 静默丢弃
 * - 构造时确保父目录存在
 */
export declare class JsonlExporter {
    private stream;
    private closed;
    private pending;
    constructor(filePath: string, _opts?: {
        flush?: boolean;
    });
    export(record: Record<string, unknown>): void;
    flush(): Promise<void>;
    close(): Promise<void>;
}