/**
 * Formats elapsed milliseconds as "MM:SS" or "HH:MM:SS" if over an hour.
 */
export function formatElapsed(ms: number): string {
  const totalSeconds = Math.floor(ms / 1000);
  const hours = Math.floor(totalSeconds / 3600);
  const minutes = Math.floor((totalSeconds % 3600) / 60);
  const seconds = totalSeconds % 60;

  const pad = (n: number) => n.toString().padStart(2, "0");

  if (hours > 0) {
    return `${pad(hours)}:${pad(minutes)}:${pad(seconds)}`;
  }
  return `${pad(minutes)}:${pad(seconds)}`;
}