feat: Complete plugin lifecycle management with lazy loading and runtime reload

Major changes:
- Add unload() method to all plugins for proper cleanup (unregister commands/providers/LSP clients, destroy widgets, clear state)
- Implement lazy widget loading via "show" signal across all containers
- Add autoload: false manifest option for manual/conditional plugin loading
- Add Plugins UI with runtime load/unload toggle via Ctrl+Shift+p
- Implement controller unregistration system with proper signal disconnection
- Add new events: UnregisterCommandEvent, GetFilesEvent, GetSourceViewsEvent, TogglePluginsUiEvent
- Fix signal leaks by tracking and disconnecting handlers in widgets (search/replace, LSP manager, tabs, telescope, markdown preview)
- Add Save/Save As to tabs context menu
- Improve search/replace behavior (selection handling, focus management)
- Add telescope file initialization from existing loaded files
- Refactor plugin reload watcher to dynamically add/remove plugins on filesystem changes
- Add new plugins: file_history, extend_source_view_menu, godot_lsp_client
- Fix bug in prettify_json (undefined variable reference

src/core/containers/body_container.py

@@ -19,7 +19,6 @@ class BodyContainer(Gtk.Box):
         self._setup_styling()
         self._setup_signals()
         self._subscribe_to_events()
-        self._load_widgets()
 
         self.show()
 
@@ -29,14 +28,17 @@ class BodyContainer(Gtk.Box):
         self.ctx.add_class("body-container")
 
         self.set_orientation(Gtk.Orientation.HORIZONTAL)
-        self.set_homogeneous(True)
 
     def _setup_signals(self):
-        ...
+        self.connect("show", self._handle_show)
 
     def _subscribe_to_events(self):
         ...
 
+    def _handle_show(self, widget):
+        self.disconnect_by_func( self._handle_show )
+        self._load_widgets()
+
     def _load_widgets(self):
         widget_registery.expose_object("body-container", self)