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; });
   }

ui/server.py

@@ -295,6 +295,12 @@ def status(_body):
 
 def headset_view():
     """Both eyes as SteamVR composites them (see frame_vrshot.py); PNG bytes."""
+    # Counts as work: the copy and clean-up must reach the headset that took the capture.
+    with working():
+        return _headset_view()
+
+
+def _headset_view():
     # `timeout`: VR_Init can block if SteamVR is restarting.
     out = ssh("timeout 15 python3 -", stdin=(HERE / "frame_vrshot.py").read_text(), timeout=30)
     # SteamVR prints its own notices (e.g. about vrwebhelper) on stdout too, so