WIP fixing menu rendering in CLI ASCII mode

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_dart/lib/src/engine/wolf_3d_engine_base.dart

@@ -184,6 +184,8 @@ class WolfEngine {
   void _tickDifficultyMenu(EngineInput input) {
     final menuResult = menuManager.updateDifficultySelection(input);
     if (menuResult.goBack) {
+      // Explicitly keep the engine in menu mode when leaving this screen.
+      difficulty = null;
       onGameWon();
       return;
     }