Fix nine-slice seams and inherited alpha

test/runtime/rendering/runtime_component_test.dart

@@ -116,6 +116,90 @@ void main() {
       expect(component.renderAlpha, 1);
     });
 
+    test('inherits parent alpha for prefab-like subtrees', () async {
+      final parent = RuntimeComponent(
+        node: const RuntimeNode(
+          id: 'parent',
+          type: RuntimeNodeType.panel,
+          alpha: 0.8,
+        ),
+        resources: GameResourceManager(),
+        onNodeTap: (_, __) {},
+      );
+      final child = RuntimeComponent(
+        node: const RuntimeNode(
+          id: 'child',
+          type: RuntimeNodeType.text,
+          text: 'Child',
+          alpha: 0.5,
+          color: Color(0xffffffff),
+        ),
+        resources: GameResourceManager(),
+        onNodeTap: (_, __) {},
+      );
+      parent.add(child);
+      parent.updateTree(0);
+      child.setInheritedAlpha(parent.renderAlpha);
+
+      expect(child.renderAlpha, closeTo(0.4, 0.001));
+      final text = child.children.whereType<TextComponent>().single;
+      expect(
+        ((text.textRenderer as TextPaint).style.color!).a,
+        closeTo(0.4, 0.003),
+      );
+
+      parent.setRuntimeAlpha(0.25);
+
+      expect(child.renderAlpha, closeTo(0.125, 0.001));
+      final updatedText = child.children.whereType<TextComponent>().single;
+      expect(identical(updatedText, text), isTrue);
+      expect(
+        ((updatedText.textRenderer as TextPaint).style.color!).a,
+        closeTo(0.125, 0.003),
+      );
+    });
+
+    test('propagates parent node alpha updates to child subtree', () {
+      final parent = RuntimeComponent(
+        node: const RuntimeNode(
+          id: 'parent',
+          type: RuntimeNodeType.panel,
+          alpha: 0.8,
+        ),
+        resources: GameResourceManager(),
+        onNodeTap: (_, __) {},
+      );
+      final child = RuntimeComponent(
+        node: const RuntimeNode(
+          id: 'child',
+          type: RuntimeNodeType.text,
+          text: 'Child',
+          alpha: 0.5,
+          color: Color(0xffffffff),
+        ),
+        resources: GameResourceManager(),
+        onNodeTap: (_, __) {},
+      );
+      parent.add(child);
+      parent.updateTree(0);
+      child.setInheritedAlpha(parent.renderAlpha);
+
+      parent.updateNode(
+        const RuntimeNode(
+          id: 'parent',
+          type: RuntimeNodeType.panel,
+          alpha: 0.6,
+        ),
+      );
+
+      final text = child.children.whereType<TextComponent>().single;
+      expect(child.renderAlpha, closeTo(0.3, 0.001));
+      expect(
+        ((text.textRenderer as TextPaint).style.color!).a,
+        closeTo(0.3, 0.003),
+      );
+    });
+
     test('multiplies color alpha with node and runtime alpha', () {
       expect(
         composeRuntimeColorAlpha(const Color(0xffffffff), 1).a,
@@ -183,6 +267,23 @@ void main() {
       expect(parts.last.destination, const Rect.fromLTRB(83, 112, 90, 120));
     });
 
+    test('overlaps nine-slice destination seams without changing bounds', () {
+      final parts = runtimeNineSliceRects(
+        source: const Rect.fromLTWH(0, 0, 30, 30),
+        destination: const Rect.fromLTWH(0, 0, 90, 90),
+        sliceLeft: 10,
+        sliceTop: 10,
+        sliceRight: 10,
+        sliceBottom: 10,
+        destinationOverlap: 0.5,
+      );
+
+      expect(parts.first.destination, const Rect.fromLTRB(0, 0, 10.5, 10.5));
+      expect(parts[4].destination, const Rect.fromLTRB(9.5, 9.5, 80.5, 80.5));
+      expect(parts.last.destination, const Rect.fromLTRB(79.5, 79.5, 90, 90));
+      expect(parts[4].source, const Rect.fromLTRB(10, 10, 20, 20));
+    });
+
     test('updates text alpha style without rebuilding text component', () {
       final component = RuntimeComponent(
         node: const RuntimeNode(