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/commands/nanoesq_temp_buffer/plugin.py

@@ -21,7 +21,13 @@ class Plugin(PluginCode):
         ...
 
     def load(self):
-        event = Event_Factory.create_event("register_command",
+        self._manage_signals("register_command")
+
+    def load(self):
+        self._manage_signals("unregister_command")
+
+    def _manage_signals(self, action: str):
+        event = Event_Factory.create_event(action,
             command_name = "cut_to_temp_buffer",
             command      = Handler,
             binding_mode = "held",
@@ -30,7 +36,7 @@ class Plugin(PluginCode):
 
         self.emit_to("source_views", event)
 
-        event = Event_Factory.create_event("register_command",
+        event = Event_Factory.create_event(action,
             command_name = "paste_temp_buffer",
             command      = Handler2,
             binding_mode = "held",