feat: Implement Phase A UI hierarchy foundations (closes #122, #102, #116, #118)

Parent-Child UI System (#122):
- Add parent weak_ptr to UIDrawable for hierarchy tracking
- Add setParent(), getParent(), removeFromParent() methods
- UICollection now tracks owner and sets parent on append/insert
- Auto-remove from old parent when adding to new collection

Global Position Property (#102):
- Add get_global_position() that walks up parent chain
- Expose as read-only 'global_position' property on all UI types
- Add UIDRAWABLE_PARENT_GETSETTERS macro for consistent bindings

Dirty Flag System (#116):
- Modify markDirty() to propagate up the parent chain
- Add isDirty() and clearDirty() methods for render optimization

Scene as Drawable (#118):
- Add position, visible, opacity properties to Scene
- Add setProperty()/getProperty() for animation support
- Apply scene transformations in PyScene::render()
- Fix lifecycle callbacks to clear errors when methods don't exist
- Add GameEngine::getScene() public accessor

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/unit/test_scene_properties.py

@@ -0,0 +1,174 @@
+#!/usr/bin/env python3
+"""Test Scene properties (#118: Scene as Drawable)"""
+import mcrfpy
+import sys
+
+# Create test scenes
+mcrfpy.createScene("test_scene")
+
+def test_scene_pos():
+    """Test Scene pos property"""
+    print("Testing scene pos property...")
+
+    # Create a Scene subclass to test
+    class TestScene(mcrfpy.Scene):
+        def __init__(self, name):
+            super().__init__(name)
+
+    scene = TestScene("scene_pos_test")
+
+    # Test initial position
+    pos = scene.pos
+    assert pos.x == 0.0, f"Initial pos.x should be 0.0, got {pos.x}"
+    assert pos.y == 0.0, f"Initial pos.y should be 0.0, got {pos.y}"
+
+    # Test setting position with tuple
+    scene.pos = (100.0, 200.0)
+    pos = scene.pos
+    assert pos.x == 100.0, f"pos.x should be 100.0, got {pos.x}"
+    assert pos.y == 200.0, f"pos.y should be 200.0, got {pos.y}"
+
+    # Test setting position with Vector
+    scene.pos = mcrfpy.Vector(50.0, 75.0)
+    pos = scene.pos
+    assert pos.x == 50.0, f"pos.x should be 50.0, got {pos.x}"
+    assert pos.y == 75.0, f"pos.y should be 75.0, got {pos.y}"
+
+    print("  - Scene pos property: PASS")
+
+def test_scene_visible():
+    """Test Scene visible property"""
+    print("Testing scene visible property...")
+
+    class TestScene(mcrfpy.Scene):
+        def __init__(self, name):
+            super().__init__(name)
+
+    scene = TestScene("scene_vis_test")
+
+    # Test initial visibility (should be True)
+    assert scene.visible == True, f"Initial visible should be True, got {scene.visible}"
+
+    # Test setting to False
+    scene.visible = False
+    assert scene.visible == False, f"visible should be False, got {scene.visible}"
+
+    # Test setting back to True
+    scene.visible = True
+    assert scene.visible == True, f"visible should be True, got {scene.visible}"
+
+    print("  - Scene visible property: PASS")
+
+def test_scene_opacity():
+    """Test Scene opacity property"""
+    print("Testing scene opacity property...")
+
+    class TestScene(mcrfpy.Scene):
+        def __init__(self, name):
+            super().__init__(name)
+
+    scene = TestScene("scene_opa_test")
+
+    # Test initial opacity (should be 1.0)
+    assert abs(scene.opacity - 1.0) < 0.001, f"Initial opacity should be 1.0, got {scene.opacity}"
+
+    # Test setting opacity
+    scene.opacity = 0.5
+    assert abs(scene.opacity - 0.5) < 0.001, f"opacity should be 0.5, got {scene.opacity}"
+
+    # Test clamping to 0.0
+    scene.opacity = -0.5
+    assert scene.opacity >= 0.0, f"opacity should be clamped to >= 0.0, got {scene.opacity}"
+
+    # Test clamping to 1.0
+    scene.opacity = 1.5
+    assert scene.opacity <= 1.0, f"opacity should be clamped to <= 1.0, got {scene.opacity}"
+
+    print("  - Scene opacity property: PASS")
+
+def test_scene_name():
+    """Test Scene name property (read-only)"""
+    print("Testing scene name property...")
+
+    class TestScene(mcrfpy.Scene):
+        def __init__(self, name):
+            super().__init__(name)
+
+    scene = TestScene("my_test_scene")
+
+    # Test name
+    assert scene.name == "my_test_scene", f"name should be 'my_test_scene', got {scene.name}"
+
+    # Name should be read-only (trying to set should raise)
+    try:
+        scene.name = "other_name"
+        print("  - Scene name should be read-only: FAIL")
+        sys.exit(1)
+    except AttributeError:
+        pass  # Expected
+
+    print("  - Scene name property: PASS")
+
+def test_scene_active():
+    """Test Scene active property"""
+    print("Testing scene active property...")
+
+    class TestScene(mcrfpy.Scene):
+        def __init__(self, name):
+            super().__init__(name)
+
+    scene1 = TestScene("active_test_1")
+    scene2 = TestScene("active_test_2")
+
+    # Activate scene1
+    scene1.activate()
+    assert scene1.active == True, f"scene1.active should be True after activation"
+    assert scene2.active == False, f"scene2.active should be False"
+
+    # Activate scene2
+    scene2.activate()
+    assert scene1.active == False, f"scene1.active should be False after activating scene2"
+    assert scene2.active == True, f"scene2.active should be True"
+
+    print("  - Scene active property: PASS")
+
+def test_scene_get_ui():
+    """Test Scene get_ui method"""
+    print("Testing scene get_ui method...")
+
+    class TestScene(mcrfpy.Scene):
+        def __init__(self, name):
+            super().__init__(name)
+
+    scene = TestScene("ui_test_scene")
+
+    # Get UI collection
+    ui = scene.get_ui()
+    assert ui is not None, "get_ui() should return a collection"
+
+    # Add some elements
+    ui.append(mcrfpy.Frame(pos=(10, 20), size=(100, 100)))
+    ui.append(mcrfpy.Caption(text="Test", pos=(50, 50)))
+
+    # Verify length
+    assert len(ui) == 2, f"UI should have 2 elements, got {len(ui)}"
+
+    print("  - Scene get_ui method: PASS")
+
+# Run all tests
+if __name__ == "__main__":
+    try:
+        test_scene_pos()
+        test_scene_visible()
+        test_scene_opacity()
+        test_scene_name()
+        test_scene_active()
+        test_scene_get_ui()
+
+        print("\n=== All Scene property tests passed! ===")
+        sys.exit(0)
+    except Exception as e:
+        print(f"\nFAIL: {e}")
+        import traceback
+        traceback.print_exc()
+        sys.exit(1)