feat: Integrate ProjectFileEditor into EditorManager for enhanced project file handling

- Initialized ProjectFileEditor within EditorManager to facilitate project file editing.
- Added menu options for editing project files, including loading and error handling with toast notifications.
- Updated the DrawMenuBar method to render the ProjectFileEditor interface.
- Included necessary header for ProjectFileEditor in editor_manager.h.

src/app/editor/agent/agent_chat_widget.cc

@@ -670,7 +670,8 @@ void AgentChatWidget::Draw() {
     
     ImGui::EndTabBar();
   }
-  
+
+  ImGui::PopStyleVar(4); // Pop the 4 style vars we pushed
   ImGui::End();
 }