feat(ui): port retained widget foundations

tests/AcDream.App.Tests/UI/Layout/LayoutConformanceTests.cs

@@ -139,6 +139,36 @@ public class LayoutConformanceTests
         Assert.Contains(0x40000000u, fontDids);
     }
 
+    [Fact]
+    public void VitalsBinding_ReusesAuthoredTextNodesWithoutDuplicates()
+    {
+        var layout = FixtureLoader.LoadVitals();
+        VitalsController.Bind(
+            layout,
+            () => 1f,
+            () => 1f,
+            () => 1f,
+            () => "100/100",
+            () => "90/100",
+            () => "80/100");
+
+        (uint MeterId, uint TextId)[] cases =
+        [
+            (VitalsController.Health, VitalsController.HealthText),
+            (VitalsController.Stamina, VitalsController.StaminaText),
+            (VitalsController.Mana, VitalsController.ManaText),
+        ];
+
+        foreach (var (meterId, textId) in cases)
+        {
+            var meter = Assert.IsType<UiMeter>(layout.FindElement(meterId));
+            var text = Assert.IsType<UiText>(layout.FindElement(textId));
+            Assert.Same(meter, text.Parent);
+            Assert.Single(meter.Children, child => child == text);
+            Assert.False(text.Selectable);
+        }
+    }
+
     private static void CollectFontDids(ElementInfo node, System.Collections.Generic.List<uint> acc)
     {
         if (node.FontDid != 0) acc.Add(node.FontDid);