Blame for src/update.js

// Pick up new versions on the next launch instead of the one after: when a new
// service worker takes over, reload — unless a conversion or playback is running,
// in which case wait until it's idle.
if ('serviceWorker' in navigator) {
  const hadController = !!navigator.serviceWorker.controller;
  const busy = () => !document.getElementById('ex-bar')?.classList.contains('hidden')
    || !document.getElementById('audio')?.paused;
  navigator.serviceWorker.addEventListener('controllerchange', () => {
    if (!hadController) return; // first install: nothing stale to replace
    const tryReload = () => (busy() ? setTimeout(tryReload, 3000) : location.reload());
    tryReload();
  });
}