Devices: restarting during startup starts afresh; a headset capture keeps its headset through clean-up (review round 33)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

app/main.js

@@ -194,6 +194,7 @@ function restartServer() {
       server = null;
       url = null;
       if (old) await endServer(old);
+      if (starting) await starting.catch(() => {});  // a start it cut short: then start afresh
       await load();
     })().finally(() => { restarting = null; });
   }