Add SortMemberPath to TableViewColumn for custom sorting

Author: cricketthomas

src/Columns/TableViewColumn.cs

@@ -457,7 +457,6 @@ private static void OnHeaderStyleChanged(DependencyObject d, DependencyPropertyC
 
     /// <summary>
     /// Gets or sets the member path to use for sorting instead of the default binding path.
-    /// Holds the name of the member to use for sorting, if not using the default.
     /// </summary>
     public string? SortMemberPath
     {

src/ItemsSource/ColumnSortDescription.cs

@@ -21,7 +21,7 @@ public ColumnSortDescription(TableViewColumn column,
 
     public override object? GetPropertyValue(object? item)
     {
-        // If a property name SortMemberPath was provided
+        // Use reflection-based property access when SortMemberPath is explicitly provided; otherwise, fall back to column cell content.
         if (!string.IsNullOrEmpty(PropertyName))
         {
             return base.GetPropertyValue(item);