Fix NavigationView content header grid splitting width 50/50

LayoutNodeFactory was not propagating FlexFactor from ColumnContainer
to LayoutNode, so all columns defaulted to FlexFactor=1.0 regardless
of the control's setting. The toolbar column in NavigationView's
content header now correctly sizes to content (FlexFactor=0) while
the title column takes remaining space.

Author: nickprotop

SharpConsoleUI/Controls/NavigationView/NavigationView.cs

@@ -116,7 +116,10 @@ public NavigationView()
 			_contentHeaderGrid.Margin = new Margin(0, 1, 0, 0);
 
 			_contentHeaderTitleColumn = new ColumnContainer(_contentHeaderGrid);
-			_contentHeaderToolbarColumn = new ColumnContainer(_contentHeaderGrid);
+			_contentHeaderToolbarColumn = new ColumnContainer(_contentHeaderGrid)
+			{
+				FlexFactor = 0  // Toolbar column sizes to content; title column takes remaining space
+			};
 
 			_contentHeaderTitleColumn.AddContent(_contentHeader);
 

SharpConsoleUI/Layout/LayoutNodeFactory.cs

@@ -81,6 +81,13 @@ public static LayoutNode CreateSubtree(IWindowControl control)
 				{
 					var childNode = CreateSubtree(child);
 					childNode.IsVisible = child.Visible;
+
+					// Propagate FlexFactor from ColumnContainer to LayoutNode
+					if (child is ColumnContainer column)
+					{
+						childNode.FlexFactor = column.FlexFactor;
+					}
+
 					node.AddChild(childNode);
 				}
 			}