Guard file open and device connect against conflicting state

Opening a file while connected to a device prompts to disconnect first.
Connecting to a device while a file is open prompts to save unsaved
changes, then closes the file before showing the connect dialog.

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

app_state.py

@@ -8,7 +8,7 @@ so later rebinding would only ever be seen by the module that did it.
 import configparser
 import os
 
-VERSION = "0.0.0.086"
+VERSION = "0.0.0.087"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True

main.py

@@ -1927,6 +1927,22 @@ _cov_poll_id = None
 
 def do_device_connect():
     """Opens the connect dialog and initiates a device connection."""
+    if app_state.current_file_path and not app_state.live_mode:
+        if app_state.is_dirty:
+            answer = messagebox.askyesnocancel(
+                "Unsaved Changes",
+                "The current file has unsaved changes.\n\n"
+                "Save before connecting to a device?",
+            )
+            if answer is None:
+                return
+            if answer:
+                sax_file.execute_direct_overwrite_save()
+        sax_file.reset_to_startup_state()
+        sax_file.refresh_treeview_from_dom(None)
+        wiresheet.render_components([])
+        app_state.window.title(app_state.base_window_title())
+
     connect_dialog.ConnectDialog(app_state.window, _connect_to_device)
 
 

sax_file.py

@@ -126,6 +126,19 @@ def open_file():
         messagebox.showwarning("Action Blocked", "Cannot load SAX profiles because 'Sedona home folder' configuration is missing or empty.")
         return
 
+    if app_state.live_mode:
+        answer = messagebox.askyesnocancel(
+            "Device Connected",
+            "A live device connection is active.\n\n"
+            "Disconnect from the device and open a file?\n\n"
+            "Choose Yes to disconnect and open, No to cancel.",
+        )
+        if not answer:
+            return
+        # Import here to avoid circular import at module level
+        from main import do_device_disconnect
+        do_device_disconnect()
+
     file_path = filedialog.askopenfilename(
         title="Select SAX File",
         filetypes=[("SAX Files", "*.sax"), ("XML Files", "*.xml"), ("All Files", "*.*")],