// Run only on the local HTTP fixture's first origin. No microphone or upload.
async function loadTeachingTrack(mediaURL, trackURL, timeoutMs = 5000) {
  const media = document.createElement('video');
  media.crossOrigin = 'anonymous';
  media.preload = 'metadata';
  media.muted = true;
  const track = document.createElement('track');
  track.kind = 'subtitles'; track.srclang = 'fa'; track.label = 'متن آزمایشی';
  const result = await new Promise(resolve => {
    let timer;
    const finish = event => {
      clearTimeout(timer);
      track.onload = track.onerror = null;
      resolve({event, readyState: track.readyState,
        cueCount: track.track.cues ? track.track.cues.length : null,
        cues: track.track.cues ? Array.from(track.track.cues, c =>
          ({id:c.id, start:c.startTime, end:c.endTime, text:c.text})) : []});
    };
    track.onload = () => finish('load'); track.onerror = () => finish('error');
    timer = setTimeout(() => finish('timeout'), timeoutMs);
    media.src = mediaURL; track.src = trackURL;
    media.append(track); document.body.append(media);
    track.track.mode = 'hidden'; media.load();
  });
  media.pause(); media.removeAttribute('src'); media.load(); media.remove();
  return result;
}