Add a Properties view for the app root

The root tree row now names the app component, "app (<host:port>)" or
"app (<file>)", and offers Properties from its context menu and on
double-click. The live DOM's <app> element now carries its type and slot
values, and the refresh-by-id lookup finds it, so the view shows real
sys::App values.

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

main.py

@@ -293,7 +293,8 @@ def show_properties(comp):
     )
     properties_panel.frame.pack(fill=tk.BOTH, expand=True)
     record_visit(VIEW_PROPERTIES, comp)
-    app_state.set_status(f"Properties: {comp.get('name', '?')}")
+    default_name = "App" if comp.tag == "app" else "?"
+    app_state.set_status(f"Properties: {comp.get('name', default_name)}")
 
 
 def dismiss_properties(restore_canvas=True):
@@ -1064,6 +1065,12 @@ def on_tree_right_click(event):
 
     if parent_id == "":
         tree_root_context_menu.delete(0, tk.END)
+        # The root row names the <app> itself, which has slots of its own to show.
+        app_element = app_state.tree_element_map.get(item_id)
+        if app_element is not None:
+            tree_root_context_menu.add_command(
+                label="Properties", command=lambda: show_properties(app_element))
+            tree_root_context_menu.add_separator()
         if app_state.live_mode and app_state.device_session and app_state.device_session.is_connected:
             for action_name in _APP_ACTIONS:
                 tree_root_context_menu.add_command(
@@ -1100,10 +1107,14 @@ def on_tree_double_click(event):
     """Double-click on a tree node opens its special view (or Properties)."""
     tree = app_state.tree
     item_id = tree.identify_row(event.y)
-    if not item_id or tree.parent(item_id) == "":
+    if not item_id:
         return
     comp = app_state.tree_element_map.get(item_id)
-    if comp is not None:
+    if comp is None:
+        return
+    if tree.parent(item_id) == "":
+        show_properties(comp)
+    else:
         _open_special_view(comp)