fix: complete retail parity stability pass

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

@@ -182,40 +182,40 @@ public class ElementReaderTests
     // ── HJustify / VJustify — Merge propagation ─────────────────────────────
 
     /// <summary>
-    /// When the derived element has a non-Center HJustify, the derived value wins
-    /// (same "non-default wins" rule as FontDid).
+    /// Authored justification is presence-based: raw 3 on the derived element
+    /// overrides raw 1 on its base.
     /// </summary>
     [Fact]
     public void Merge_DerivedHJustifyRight_OverridesBaseCenter()
     {
-        var base_   = new ElementInfo { HJustify = HJustify.Center };
-        var derived = new ElementInfo { HJustify = HJustify.Right };
+        ElementInfo base_ = WithJustification(0x14u, 1u);
+        ElementInfo derived = WithJustification(0x14u, 3u);
         var merged  = ElementReader.Merge(base_, derived);
         Assert.Equal(HJustify.Right, merged.HJustify);
     }
 
     /// <summary>
-    /// When the derived element has the default HJustify (Center), the base value
-    /// is inherited — Center from the derived does NOT override a Left base.
+    /// Center is a real authored raw value, not an unset sentinel, and must
+    /// therefore override a Left base.
     /// </summary>
     [Fact]
-    public void Merge_DerivedHJustifyCenter_InheritsBaseLeft()
+    public void Merge_DerivedAuthoredHJustifyCenter_OverridesBaseLeft()
     {
-        var base_   = new ElementInfo { HJustify = HJustify.Left };
-        var derived = new ElementInfo { HJustify = HJustify.Center };   // default — no explicit dat property
+        ElementInfo base_ = WithJustification(0x14u, 2u);
+        ElementInfo derived = WithJustification(0x14u, 1u);
         var merged  = ElementReader.Merge(base_, derived);
-        Assert.Equal(HJustify.Left, merged.HJustify);
+        Assert.Equal(HJustify.Center, merged.HJustify);
     }
 
     /// <summary>
-    /// VJustify=Top from the base propagates when the derived element has no explicit
-    /// (Center) vertical justification.
+    /// VJustify=Top from the base propagates when the derived element authors
+    /// no vertical justification.
     /// </summary>
     [Fact]
-    public void Merge_BaseVJustifyTop_InheritedWhenDerivedIsCenter()
+    public void Merge_BaseVJustifyTop_InheritedWhenDerivedIsUnauthored()
     {
-        var base_   = new ElementInfo { VJustify = VJustify.Top };
-        var derived = new ElementInfo { VJustify = VJustify.Center };   // default
+        ElementInfo base_ = WithJustification(0x15u, 4u);
+        var derived = new ElementInfo();
         var merged  = ElementReader.Merge(base_, derived);
         Assert.Equal(VJustify.Top, merged.VJustify);
     }
@@ -226,8 +226,8 @@ public class ElementReaderTests
     [Fact]
     public void Merge_DerivedVJustifyBottom_OverridesBaseCenter()
     {
-        var base_   = new ElementInfo { VJustify = VJustify.Center };
-        var derived = new ElementInfo { VJustify = VJustify.Bottom };
+        ElementInfo base_ = WithJustification(0x15u, 1u);
+        ElementInfo derived = WithJustification(0x15u, 3u);
         var merged  = ElementReader.Merge(base_, derived);
         Assert.Equal(VJustify.Bottom, merged.VJustify);
     }
@@ -380,6 +380,54 @@ public class ElementReaderTests
         return info;
     }
 
+    private static ElementInfo WithJustification(uint propertyId, uint raw)
+    {
+        ElementInfo info = WithDirectProperty(propertyId, EnumProp(raw));
+        ElementReader.ApplyCanonicalLegacyProjection(info);
+        return info;
+    }
+
+    [Fact]
+    public void Justification_UnauthoredDefaultsMatchRetailConstructors()
+    {
+        var info = new ElementInfo();
+
+        Assert.Equal(HJustify.Left, info.HJustify);
+        Assert.Equal(VJustify.Top, info.VJustify);
+    }
+
+    [Theory]
+    [InlineData(0u, HJustify.Left)]
+    [InlineData(1u, HJustify.Center)]
+    [InlineData(2u, HJustify.Left)]
+    [InlineData(3u, HJustify.Right)]
+    [InlineData(4u, HJustify.Left)]
+    [InlineData(5u, HJustify.Right)]
+    public void HorizontalJustification_AllRetailRawValues(
+        uint raw,
+        HJustify expected)
+    {
+        ElementInfo info = WithJustification(0x14u, raw);
+
+        Assert.Equal(expected, info.HJustify);
+    }
+
+    [Theory]
+    [InlineData(0u, VJustify.Top)]
+    [InlineData(1u, VJustify.Center)]
+    [InlineData(2u, VJustify.Top)]
+    [InlineData(3u, VJustify.Bottom)]
+    [InlineData(4u, VJustify.Top)]
+    [InlineData(5u, VJustify.Bottom)]
+    public void VerticalJustification_AllRetailRawValues(
+        uint raw,
+        VJustify expected)
+    {
+        ElementInfo info = WithJustification(0x15u, raw);
+
+        Assert.Equal(expected, info.VJustify);
+    }
+
     [Fact]
     public void ReadTabTable_DecodesButtonPageDefaultInAuthoredOrder()
     {