fix: Register keypressScene after setScene (closes #143)

keypressScene() sets the handler for the CURRENT scene, so we must
call setScene() first to make focus_demo the active scene before
registering the key handler.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/demo/screens/focus_system_demo.py

@@ -751,17 +751,15 @@ def create_demo_scene():
         else:
             status_text.text = "No widget focused"
 
-    # Register key handler using Scene API
-    scene = mcrfpy.sceneUI("focus_demo")
-    # Note: We use keypressScene for function-based handler since we're not subclassing Scene
+    # Activate scene first (keypressScene sets handler for CURRENT scene)
+    mcrfpy.setScene("focus_demo")
+
+    # Register key handler for the now-current scene
     mcrfpy.keypressScene(on_key)
 
     # Set initial focus
     focus_mgr.focus(0)
 
-    # Activate scene
-    mcrfpy.setScene("focus_demo")
-
     return demo_state