feat: Refactor editor structure and enhance multi-session support

- Moved `menu_builder.cc` to a new `ui` directory for better organization.
- Updated `EditorManager` to generate unique ImGui IDs for multi-session support, ensuring separate window handling.
- Added session ID management in `EditorContext` for improved child panel identification.
- Introduced a new `MenuBuilder` class for streamlined ImGui menu creation, enhancing UI maintainability.

src/app/editor/ui/menu_builder.h

@@ -0,0 +1,119 @@
+#ifndef YAZE_APP_EDITOR_UI_MENU_BUILDER_H_
+#define YAZE_APP_EDITOR_UI_MENU_BUILDER_H_
+
+#include <functional>
+#include <string>
+#include <vector>
+
+#include "app/gui/icons.h"
+#include "imgui/imgui.h"
+
+namespace yaze {
+namespace editor {
+
+/**
+ * @class MenuBuilder
+ * @brief Fluent interface for building ImGui menus with icons
+ * 
+ * Provides a cleaner, more maintainable way to construct menus:
+ * 
+ * MenuBuilder menu;
+ * menu.BeginMenu("File", ICON_MD_FOLDER)
+ *     .Item("Open", ICON_MD_FILE_OPEN, []() { OpenFile(); })
+ *     .Separator()
+ *     .Item("Quit", ICON_MD_EXIT_TO_APP, []() { Quit(); })
+ *     .EndMenu();
+ */
+class MenuBuilder {
+ public:
+  using Callback = std::function<void()>;
+  using EnabledCheck = std::function<bool()>;
+  
+  MenuBuilder() = default;
+  
+  /**
+   * @brief Begin a top-level menu
+   */
+  MenuBuilder& BeginMenu(const char* label, const char* icon = nullptr);
+  
+  /**
+   * @brief Begin a submenu
+   */
+  MenuBuilder& BeginSubMenu(const char* label, const char* icon = nullptr,
+                            EnabledCheck enabled = nullptr);
+  
+  /**
+   * @brief End the current menu/submenu
+   */
+  MenuBuilder& EndMenu();
+  
+  /**
+   * @brief Add a menu item
+   */
+  MenuBuilder& Item(const char* label, const char* icon, Callback callback,
+                    const char* shortcut = nullptr,
+                    EnabledCheck enabled = nullptr,
+                    EnabledCheck checked = nullptr);
+  
+  /**
+   * @brief Add a menu item without icon (convenience)
+   */
+  MenuBuilder& Item(const char* label, Callback callback,
+                    const char* shortcut = nullptr,
+                    EnabledCheck enabled = nullptr);
+  
+  /**
+   * @brief Add a separator
+   */
+  MenuBuilder& Separator();
+  
+  /**
+   * @brief Add a disabled item (grayed out)
+   */
+  MenuBuilder& DisabledItem(const char* label, const char* icon = nullptr);
+  
+  /**
+   * @brief Draw the menu bar (call in main menu bar)
+   */
+  void Draw();
+  
+  /**
+   * @brief Clear all menus
+   */
+  void Clear();
+  
+ private:
+  struct MenuItem {
+    enum class Type {
+      kItem,
+      kSubMenuBegin,
+      kSubMenuEnd,
+      kSeparator,
+      kDisabled
+    };
+    
+    Type type;
+    std::string label;
+    std::string icon;
+    std::string shortcut;
+    Callback callback;
+    EnabledCheck enabled;
+    EnabledCheck checked;
+  };
+  
+  struct Menu {
+    std::string label;
+    std::string icon;
+    std::vector<MenuItem> items;
+  };
+  
+  std::vector<Menu> menus_;
+  Menu* current_menu_ = nullptr;
+  
+  void DrawMenuItem(const MenuItem& item);
+};
+
+}  // namespace editor
+}  // namespace yaze
+
+#endif  // YAZE_APP_EDITOR_UI_MENU_BUILDER_H_