Fix connect dialog: button order and cancel-during-connection cleanup

Swap Connect/Cancel button order so Connect is the default (leftmost).
Guard background thread against cancelled state so a cancelled connect
does not leave the app in live mode. Cancel during connection now
disconnects the session cleanly in a cleanup thread.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

connect_dialog.py

@@ -64,12 +64,12 @@ class ConnectDialog:
         btn_frame = ttk.Frame(frame)
         btn_frame.grid(row=row, column=0, columnspan=3, sticky="e", pady=(8, 0))
 
-        self._btn_connect = ttk.Button(btn_frame, text="Connect", command=self._do_connect)
-        self._btn_connect.pack(side=tk.RIGHT, padx=(8, 0))
-
         self._btn_cancel = ttk.Button(btn_frame, text="Cancel", command=self._do_cancel)
         self._btn_cancel.pack(side=tk.RIGHT)
 
+        self._btn_connect = ttk.Button(btn_frame, text="Connect", command=self._do_connect)
+        self._btn_connect.pack(side=tk.RIGHT, padx=(0, 8))
+
         self._host_entry.focus_set()
         self._dlg.bind("<Return>", lambda e: self._do_connect())
         self._dlg.bind("<Escape>", lambda e: self._do_cancel())
@@ -110,8 +110,12 @@ class ConnectDialog:
     def _connect_worker(self, host, port, user, password):
         try:
             result = self._callback(host, port, user, password)
+            if self._cancelled:
+                return
             self._result = ("ok", result, host, port, user)
         except Exception as e:
+            if self._cancelled:
+                return
             self._result = ("error", str(e), host, port, user)
 
     def _poll_connect(self):
@@ -133,6 +137,20 @@ class ConnectDialog:
 
     def _do_cancel(self):
         self._cancelled = True
+        if self._thread is not None and self._thread.is_alive():
+            # Connection attempt in progress — clean up after it finishes
+            import app_state as _as
+            def _cleanup():
+                self._thread.join(timeout=5)
+                if _as.device_session is not None and _as.live_mode:
+                    try:
+                        _as.device_session.disconnect()
+                    except Exception:
+                        pass
+                    _as.live_mode = False
+                    _as.device_session = None
+                    _as.connection_status = "offline"
+            threading.Thread(target=_cleanup, daemon=True).start()
         self._dlg.destroy()