feat: Enhance AgentChatWidget with system prompt management and project settings

- Updated system prompt loading functionality to support both version 1 and version 2 prompts, allowing users to load built-in prompts directly.
- Implemented custom system prompt loading and saving capabilities, enabling users to manage their prompts more effectively.
- Added methods to load and save agent settings from/to project files, including AI provider configurations and custom prompts.
- Improved user feedback with toast notifications for successful and failed operations related to system prompts and settings.

src/app/editor/agent/agent_chat_widget.h

@@ -12,6 +12,7 @@
 #include "absl/time/time.h"
 #include "app/gui/modules/text_editor.h"
 #include "cli/service/agent/conversational_agent_service.h"
+#include "core/project.h"
 
 namespace yaze {
 
@@ -176,6 +177,10 @@ public:
   // Agent configuration accessors
   const AgentConfigState& GetAgentConfig() const { return agent_config_; }
   void UpdateAgentConfig(const AgentConfigState& config);
+  
+  // Load agent settings from project
+  void LoadAgentSettingsFromProject(const core::YazeProject& project);
+  void SaveAgentSettingsToProject(core::YazeProject& project);
 
   // Collaboration history management (public so EditorManager can call them)
   void SwitchToSharedHistory(const std::string& session_id);