feat(ui): port retained widget foundations

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

@@ -42,7 +42,42 @@ public class DatWidgetFactoryTests
     public void Type12_Text_MakesUiText()
     {
         var e = DatWidgetFactory.Create(new ElementInfo { Type = 12, Width = 100, Height = 40 }, NoTex, null);
-        Assert.IsType<UiText>(e);
+        var text = Assert.IsType<UiText>(e);
+        Assert.False(text.Selectable);
+        Assert.True(text.ClickThrough);
+        Assert.False(text.AcceptsFocus);
+        Assert.False(text.CapturesPointerDrag);
+    }
+
+    [Fact]
+    public void Type12_EditableProperty_MakesUiFieldInPlace()
+    {
+        var info = TextInfo(
+            (0x16u, Bool(true)),
+            (0x20u, Bool(true)),
+            (0x27u, Bool(true)),
+            (0x1Eu, Integer(80)));
+
+        var field = Assert.IsType<UiField>(DatWidgetFactory.Create(info, NoTex, null));
+
+        Assert.Equal(info.Id, field.ElementId);
+        Assert.True(field.OneLine);
+        Assert.True(field.Selectable);
+        Assert.Equal(80, field.MaxCharacters);
+    }
+
+    [Fact]
+    public void Type12_SelectableProperty_MakesSelectableUiText()
+    {
+        var text = Assert.IsType<UiText>(DatWidgetFactory.Create(
+            TextInfo((0x27u, Bool(true))),
+            NoTex,
+            null));
+
+        Assert.True(text.Selectable);
+        Assert.False(text.ClickThrough);
+        Assert.True(text.AcceptsFocus);
+        Assert.True(text.CapturesPointerDrag);
     }
 
     // ── Test 4: Rect + anchors set from ElementInfo ───────────────────────────
@@ -74,6 +109,46 @@ public class DatWidgetFactoryTests
         Assert.Equal(AnchorEdges.Left | AnchorEdges.Top | AnchorEdges.Right, e.Anchors);
     }
 
+    [Fact]
+    public void ImportedDescendant_PreservesExactRawEdgePolicy()
+    {
+        var info = new ElementInfo
+        {
+            Type = 3,
+            X = 10,
+            Y = 20,
+            Width = 30,
+            Height = 40,
+            Left = 4,
+            Top = 3,
+            Right = 1,
+            Bottom = 0,
+            OriginalParentWidth = 100,
+            OriginalParentHeight = 200,
+            HasOriginalParentSize = true,
+        };
+
+        var element = DatWidgetFactory.Create(info, NoTex, null)!;
+        var policy = Assert.IsType<UiLayoutPolicy>(element.LayoutPolicy);
+
+        Assert.Equal(4u, policy.LeftMode);
+        Assert.Equal(3u, policy.TopMode);
+        Assert.Equal(1u, policy.RightMode);
+        Assert.Equal(0u, policy.BottomMode);
+        Assert.Equal(new UiPixelRect(0, 0, 99, 199), policy.OriginalParent);
+    }
+
+    [Fact]
+    public void ImportedRoot_HasNoRawEdgePolicy()
+    {
+        var element = DatWidgetFactory.Create(
+            new ElementInfo { Type = 3, Width = 100, Height = 200 },
+            NoTex,
+            null)!;
+
+        Assert.Null(element.LayoutPolicy);
+    }
+
     [Fact]
     public void Create_PropagatesStateCursors()
     {
@@ -339,6 +414,22 @@ public class DatWidgetFactoryTests
         Assert.Equal(gold, t.DefaultColor);
     }
 
+    private static ElementInfo TextInfo(params (uint Id, UiPropertyValue Value)[] properties)
+    {
+        var info = new ElementInfo { Id = 0x10000016u, Type = 12, Width = 100, Height = 20 };
+        var state = new UiStateInfo { Id = UiStateInfo.DirectStateId };
+        foreach (var property in properties)
+            state.Properties.Values[property.Id] = property.Value;
+        info.States[UiStateInfo.DirectStateId] = state;
+        return info;
+    }
+
+    private static UiPropertyValue Bool(bool value)
+        => new() { Kind = UiPropertyKind.Bool, BoolValue = value };
+
+    private static UiPropertyValue Integer(int value)
+        => new() { Kind = UiPropertyKind.Integer, IntegerValue = value };
+
     /// <summary>
     /// When ElementInfo.FontColor is null (dat carried no 0x1B), DefaultColor must
     /// stay at white (Vector4.One) — the backward-compatible default.