fix(window): ensure SDL3/Wayland window is mapped by pumping events after ShowWindow

- Remove ALWAYS_ON_TOP and debug print hacks.
- Pump SDL events after SDL_ShowWindow so the Wayland compositor maps the window.
- Clean run.sh: do not force DISPLAY or SDL_VIDEODRIVER, let SDL3 auto-detect.

src/Engine.Core/Sdl3Window.cs

@@ -46,6 +46,11 @@ public sealed unsafe class Sdl3Window : IWindow
 
         SDL3.SDL_ShowWindow(_window);
         SDL3.SDL_RaiseWindow(_window);
+
+        // On Wayland, the compositor needs an event round-trip before mapping
+        // the window. Pump events to flush the show request without blocking.
+        SDL_Event flushEvt;
+        while (SDL3.SDL_PollEvent(&flushEvt)) { }
     }
 
     public void PumpEvents()