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/language_server_clients/lsp_manager/plugin.py

@@ -62,6 +62,31 @@ class Plugin(PluginCode):
         source_view = event.response
         lsp_manager.lsp_manager_ui.set_source_view(source_view)
 
+    def unload(self):
+        Event_Factory.unregister_events( lsp_events.__dict__.items() )
+
+        self.unregister_controller("lsp_manager")
+
+        window = self.request_ui_element("main-window")
+
+        lsp_manager.lsp_manager_ui.unmap_parent_resize_event(window)
+
+        event  = Event_Factory.create_event("unregister_command",
+            command_name = "LSP Manager",
+            command      = Handler,
+            binding_mode = "released",
+            binding      = ["<Shift><Control>l", "<Control>g", "<Control>i"]
+        )
+        self.emit_to("source_views", event)
+
+        event  = Event_Factory.create_event(
+            "unregister_provider",
+            provider_name = "LSP Completer"
+        )
+        self.emit_to("completion", event)
+
+        lsp_manager.handle_destroy()
+
     def run(self):
         ...