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

plugins/code/ui/tabs_bar/tab_widget.py

@@ -32,7 +32,6 @@ class TabWidget(Gtk.Box):
         self.set_orientation(0)
         self.set_hexpand(False)
         self.set_vexpand(False)
-        self.set_can_focus(False)
         self.set_size_request(-1, 12)
 
     def _setup_signals(self):
@@ -44,10 +43,6 @@ class TabWidget(Gtk.Box):
         self.close_bttn = Gtk.Button()
         icon            = Gtk.Image(stock = Gtk.STOCK_CLOSE)
 
-        self.event_box.set_can_focus(False)
-        self.label.set_can_focus(False)
-        self.close_bttn.set_can_focus(False)
-
         self.event_box.set_above_child(True)
         ctx = self.label.get_style_context()
         ctx.add_class("tab-label")