Connect to another device without disconnecting first

Connect and Discover stay enabled while a device is connected. Pressing
Connect in the dialog drops the current device before the new one is
tried; cancelling the dialog leaves the connection alone.

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

main.py

@@ -2316,7 +2316,8 @@ def do_device_connect():
         wiresheet.render_components([])
         app_state.window.title(app_state.base_window_title())
 
-    connect_dialog.ConnectDialog(app_state.window, _connect_to_device)
+    connect_dialog.ConnectDialog(app_state.window, _connect_to_device,
+                                 on_before_connect=_drop_device_before_connect)
 
 
 def do_device_discover():
@@ -2337,7 +2338,18 @@ def do_device_discover():
         wiresheet.render_components([])
         app_state.window.title(app_state.base_window_title())
 
-    connect_dialog.DiscoverDialog(app_state.window, _connect_to_device)
+    connect_dialog.DiscoverDialog(app_state.window, _connect_to_device,
+                                  on_before_connect=_drop_device_before_connect)
+
+
+def _drop_device_before_connect():
+    """One device at a time: the one already connected goes before the next is tried.
+
+    Called when Connect is pressed, not when the dialog opens, so backing out of the
+    dialog leaves the current connection alone.
+    """
+    if app_state.device_session is not None:
+        do_device_disconnect()
 
 
 def _connect_to_device(host, port, user, password):
@@ -2358,8 +2370,6 @@ def _connect_to_device(host, port, user, password):
 def _on_connected(ds, root_comp):
     """Main-thread callback after successful connect."""
     app_state.window.title(app_state.base_window_title_live())
-    menu_device.entryconfig("Connect...", state="disabled")
-    menu_device.entryconfig("Discover...", state="disabled")
     menu_device.entryconfig("Disconnect", state="normal")
     menu_device.entryconfig("Download to SAX...", state="normal")
     app_state.set_status(f"Connected to {app_state.device_host}:{app_state.device_port}")