Restart from the tree no longer hangs for 30 s on disconnect

With a wiresheet open, disconnecting first unsubscribed its components and
waited for the reply, which a restarting device never sends, so the editor
froze until the request timed out. After restart, reboot, quit or hibernate
the session is now closed without asking the device anything; a plain
Disconnect still unsubscribes first.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

main.py

@@ -636,7 +636,7 @@ def _invoke_app_action(slot_name):
         app_state.set_status(f"Invoked '{slot_name}' on device")
     elif goes_down:
         host = app_state.device_host
-        do_device_disconnect()
+        do_device_disconnect(device_down=True)
         app_state.set_status(f"Sent '{slot_name}' to {host} and disconnected")
     else:
         app_state.set_status(f"Invoked '{slot_name}' on device")
@@ -2996,8 +2996,9 @@ def _load_live_schema(ds):
             f"Missing kit manifests: {', '.join(missing)}", warn=True)
 
 
-def do_device_disconnect():
-    """Disconnects from the live device."""
+def do_device_disconnect(device_down=False):
+    """Disconnects from the live device. device_down: it was just told to restart (or
+    stop), so nothing is asked of it on the way out -- it would not answer."""
     global _cov_poll_id
 
     if _cov_poll_id is not None:
@@ -3006,7 +3007,7 @@ def do_device_disconnect():
 
     ds = app_state.device_session
     if ds is not None:
-        ds.disconnect()
+        ds.disconnect(unsubscribe=not device_down)
 
     app_state.device_session = None
     app_state.live_mode = False