feat: Enhance project file management and agent settings

- Added support for loading and saving agent settings in the project format, including AI provider, model, and custom prompts.
- Implemented RecentFilesManager for managing recent files with functionality to save and load recent file paths.
- Introduced a new ProjectFileEditor for editing .yaze project files with syntax highlighting and validation features.
- Enhanced the AgentChatWidget with file editing capabilities, allowing users to open, create, and save files directly within the interface.
- Improved configuration directory handling and path expansion for better cross-platform compatibility.

src/app/editor/code/project_file_editor.h

@@ -0,0 +1,95 @@
+#ifndef YAZE_APP_EDITOR_CODE_PROJECT_FILE_EDITOR_H_
+#define YAZE_APP_EDITOR_CODE_PROJECT_FILE_EDITOR_H_
+
+#include <string>
+
+#include "absl/status/status.h"
+#include "app/core/project.h"
+#include "app/gui/modules/text_editor.h"
+
+namespace yaze {
+namespace editor {
+
+class ToastManager;
+
+/**
+ * @class ProjectFileEditor
+ * @brief Editor for .yaze project files with syntax highlighting and validation
+ * 
+ * Provides a rich text editing experience for yaze project files with:
+ * - Syntax highlighting for INI-style format
+ * - Real-time validation
+ * - Auto-save capability
+ * - Integration with core::YazeProject
+ */
+class ProjectFileEditor {
+ public:
+  ProjectFileEditor();
+  
+  void Draw();
+  
+  /**
+   * @brief Load a project file into the editor
+   */
+  absl::Status LoadFile(const std::string& filepath);
+  
+  /**
+   * @brief Save the current editor contents to disk
+   */
+  absl::Status SaveFile();
+  
+  /**
+   * @brief Save to a new file path
+   */
+  absl::Status SaveFileAs(const std::string& filepath);
+  
+  /**
+   * @brief Get whether the file has unsaved changes
+   */
+  bool IsModified() const { return text_editor_.IsTextChanged() || modified_; }
+  
+  /**
+   * @brief Get the current filepath
+   */
+  const std::string& filepath() const { return filepath_; }
+  
+  /**
+   * @brief Set whether the editor window is active
+   */
+  void set_active(bool active) { active_ = active; }
+  
+  /**
+   * @brief Get pointer to active state for ImGui
+   */
+  bool* active() { return &active_; }
+  
+  /**
+   * @brief Set toast manager for notifications
+   */
+  void SetToastManager(ToastManager* toast_manager) {
+    toast_manager_ = toast_manager;
+  }
+  
+  /**
+   * @brief Create a new empty project file
+   */
+  void NewFile();
+  
+ private:
+  void ApplySyntaxHighlighting();
+  void ValidateContent();
+  void ShowValidationErrors();
+  
+  TextEditor text_editor_;
+  std::string filepath_;
+  bool active_ = false;
+  bool modified_ = false;
+  bool show_validation_ = true;
+  std::vector<std::string> validation_errors_;
+  ToastManager* toast_manager_ = nullptr;
+};
+
+}  // namespace editor
+}  // namespace yaze
+
+#endif  // YAZE_APP_EDITOR_CODE_PROJECT_FILE_EDITOR_H_