feat(display): add Pygame native window display backend

- Add PygameDisplay for rendering in native application window
- Add pygame to optional dependencies
- Add run-pygame mise task

engine/display/__init__.py

@@ -10,6 +10,7 @@ from typing import Protocol
 from engine.display.backends.kitty import KittyDisplay
 from engine.display.backends.multi import MultiDisplay
 from engine.display.backends.null import NullDisplay
+from engine.display.backends.pygame import PygameDisplay
 from engine.display.backends.sixel import SixelDisplay
 from engine.display.backends.terminal import TerminalDisplay
 from engine.display.backends.websocket import WebSocketDisplay
@@ -78,6 +79,7 @@ class DisplayRegistry:
         cls.register("websocket", WebSocketDisplay)
         cls.register("sixel", SixelDisplay)
         cls.register("kitty", KittyDisplay)
+        cls.register("pygame", PygameDisplay)
 
         cls._initialized = True