// Formats seconds as `m:ss` or `h:mm:ss`. NaN/Infinity → "0:00".
export function formatTime(seconds: number): string {
  if (!Number.isFinite(seconds) || seconds < 0) return '0:00';
  const total = Math.floor(seconds);
  const s = total % 60;
  const m = Math.floor(total / 60) % 60;
  const h = Math.floor(total / 3600);
  const ss = s.toString().padStart(2, '0');
  if (h > 0) {
    const mm = m.toString().padStart(2, '0');
    return `${h}:${mm}:${ss}`;
  }
  return `${m}:${ss}`;
}