Function makeFileOutput

src/commands/test.ts:7808–7821

* Adapter that turns a `FileSink` into the `Output` writer set. Both * `print` (line-oriented JSON) and `writeChunk` (raw bytes) flow into * the same stream; backpressure is preserved on the chunk path by * resolving the returned promise on `'drain'` when the kernel buffer * is full, mirroring t

(mode: OutputMode, sink: FileSink)

 * is full, mirroring the stdout writer in `output.ts`.
 */
function makeFileOutput(mode: OutputMode, sink: FileSink): Output {
  return new Output(mode, {
    stdout: line => {
      sink.stream.write(`${line}\n`);
    },
    rawStdout: text => {
      if (sink.error) throw sink.error;
      if (sink.stream.write(text)) return;
      return new Promise<void>(resolve => {
        sink.stream.once('drain', () => resolve());
      });
    },
  });
}

/**
 * Flush + close the file sink. Called on the success path after the