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/provider/provider_response_cache.py

@@ -15,27 +15,27 @@ class ProviderResponseCache(ProviderResponseCacheBase):
     def __init__(self):
         super(ProviderResponseCache, self).__init__()
 
-        self.matchers: dict = {}
-        self._lsp_client = None
+        self.matchers: dict     = {}
+        self.lsp_manager_client = None
 
-    def set_lsp_client(self, lsp_client):
-        self._lsp_client = lsp_client
+    def set_lsp_manager_client(self, lsp_client):
+        self.lsp_manager_client = lsp_client
 
     def process_file_load(self, event):
-        if self._lsp_client:
-            self._lsp_client.process_file_load(event)
+        if self.lsp_manager_client:
+            self.lsp_manager_client.process_file_load(event)
 
     def process_file_close(self, event):
-        if self._lsp_client:
-            self._lsp_client.process_file_close(event)
+        if self.lsp_manager_client:
+            self.lsp_manager_client.process_file_close(event)
 
     def process_file_save(self, event):
-        if self._lsp_client:
-            self._lsp_client.process_file_save(event)
+        if self.lsp_manager_client:
+            self.lsp_manager_client.process_file_save(event)
 
     def process_file_change(self, event):
-        if self._lsp_client:
-            self._lsp_client.process_file_change(event)
+        if self.lsp_manager_client:
+            self.lsp_manager_client.process_file_change(event)
 
     def filter(self, word: str) -> list[dict]:
         return []