[refactor] organize GUI code by responsibility

src/gui/platform/tray/mac_tray.h

@@ -0,0 +1,34 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2026-06-23
+ * Copyright (c) 2026 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _MAC_TRAY_H_
+#define _MAC_TRAY_H_
+
+#include <memory>
+#include <string>
+
+struct SDL_Window;
+
+namespace crossdesk {
+
+struct MacTrayImpl;
+
+class MacTray {
+ public:
+  MacTray(::SDL_Window* app_window, const std::string& tooltip,
+          int language_index);
+  ~MacTray();
+
+  void MinimizeToTray();
+  void RemoveTrayIcon();
+
+ private:
+  std::unique_ptr<MacTrayImpl> impl_;
+};
+
+}  // namespace crossdesk
+
+#endif  // _MAC_TRAY_H_