fade effect when switching states

src/states/State.h

@@ -13,6 +13,7 @@ class Starfield;
 class Starfield3D;
 class FontAtlas;
 class LineEffect;
+enum class AppState;
 
 // Forward declare StateManager so StateContext can hold a pointer without
 // including the StateManager header here.
@@ -58,6 +59,7 @@ struct StateContext {
     std::function<bool()> queryFullscreen; // Optional callback if fullscreenFlag is not reliable
     std::function<void()> requestQuit; // Allows menu/option states to close the app gracefully
     std::function<void()> startPlayTransition; // Optional fade hook when transitioning from menu to gameplay
+    std::function<void(AppState)> requestFadeTransition; // Generic state fade requests (menu/options/level)
     // Pointer to the application's StateManager so states can request transitions
     StateManager* stateManager = nullptr;
 };