fix: column-wrap flex container collapses to zero height without explicit height

A flex container with direction: column + wrap: wrap and no explicit
height collapsed to ~0 height, clipping all content. The wrapped
strategy only set the cross-axis auto dimension (width for column-wrap),
never the main-axis (height), and the engine skipped fallback
height calculation for all wrap containers.

- WrappedFlexLayoutStrategy now records resolved trailing margins
  (MarginRight/MarginBottom) on wrap children so CalculateTotalHeight/
  Width account for them, matching the non-wrap strategies.
- LayoutEngine computes auto height whenever the strategy left
  node.Height unset (node.Height == 0f), covering no-wrap and
  column-wrap; row-wrap already sets height and is skipped.

Author: RoboNET

src/FlexRender.Core/Layout/LayoutEngine.cs

@@ -401,8 +401,10 @@ private LayoutNode LayoutFlexElement(FlexElement flex, LayoutContext context)
             MirrorRowXPositions(node, effectivePadding);
         }
 
-        // Calculate height if not specified (skip for wrapped containers — they set height in LayoutWrappedFlex)
-        if (height == 0f && node.Children.Count > 0 && flex.Wrap.Value == FlexWrap.NoWrap)
+        // Compute auto height when the strategy did not set it — covers no-wrap and
+        // column-wrap. Row-wrap already sets height (its cross axis), so node.Height is
+        // non-zero there and this is skipped.
+        if (height == 0f && node.Children.Count > 0 && node.Height == 0f)
         {
             node.Height = LayoutHelpers.CalculateTotalHeight(node) + effectivePadding.Bottom;
         }

src/FlexRender.Core/Layout/WrappedFlexLayoutStrategy.cs

@@ -511,6 +511,11 @@ private static void ResolveFlexForLine(LayoutNode node, FlexElement flex, Layout
             var child = lineChildren[i];
             var childMargin = PaddingParser.Parse(child.Element.Margin.Value, context.ContainerWidth, context.FontSize).ClampNegatives();
 
+            // Record resolved trailing margins so CalculateTotalHeight/Width (used for
+            // auto-sizing the container) accounts for them, matching the non-wrap strategies.
+            child.MarginRight = childMargin.Right;
+            child.MarginBottom = childMargin.Bottom;
+
             if (isColumn)
             {
                 child.Y = pos + childMargin.Top;

tests/FlexRender.Tests/Layout/LayoutEngineWrapTests.cs

@@ -418,4 +418,41 @@ public void ComputeLayout_RowWrap_EmptyChildren_NoWrap()
         Assert.Equal(100f, flexNode.Height, 0.1f);
         Assert.Empty(flexNode.Children);
     }
+
+    [Fact]
+    public void ComputeLayout_ColumnWrap_NoExplicitHeight_SizesToContentIncludingBottomMargin()
+    {
+        // Arrange: Column wrap, no explicit height, two children W=120 H=40 margin=20.
+        // Single column (no main-axis constraint): both stack on the main axis (Y).
+        // Item A: Y=20 (top margin), H=40 -> bottom edge 60, +bottom margin 20 -> 80.
+        // Item B: Y=100 (60 + bottom margin 20 + top margin 20), H=40 -> bottom edge 140, +bottom margin 20 -> 160.
+        // Container auto-height must size to content = 160 (previously collapsed to ~0).
+        var flex = new FlexElement
+        {
+            Direction = FlexDirection.Column,
+            Wrap = FlexWrap.Wrap
+        };
+        flex.AddChild(new TextElement { Content = "AAAA", Width = "120", Height = "40", Margin = "20" });
+        flex.AddChild(new TextElement { Content = "BBBB", Width = "120", Height = "40", Margin = "20" });
+
+        var template = new Template
+        {
+            Canvas = new CanvasSettings { Width = 300 },
+            Elements = new List<TemplateElement> { flex }
+        };
+
+        // Act
+        var root = _engine.ComputeLayout(template);
+
+        // Assert
+        var flexNode = root.Children[0];
+
+        Assert.Equal(20f, flexNode.Children[0].Y, 0.1f);
+        Assert.Equal(40f, flexNode.Children[0].Height, 0.1f);
+        Assert.Equal(100f, flexNode.Children[1].Y, 0.1f);
+        Assert.Equal(40f, flexNode.Children[1].Height, 0.1f);
+
+        // Container auto-height includes the trailing bottom margin of the last child.
+        Assert.Equal(160f, flexNode.Height, 0.1f);
+    }
 }