Reload into new versions when idle

src/update.js

@@ -0,0 +1,13 @@
+// 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();
+  });
+}