test: add headless test for canselect handling.

tests/HeadlessTest.Ursa/Controls/NavMenuTests/CanSelectTests/TestView2.axaml.cs

@@ -0,0 +1,43 @@
+using System.Collections.ObjectModel;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+using CommunityToolkit.Mvvm.ComponentModel;
+using Ursa.Controls;
+
+namespace HeadlessTest.Ursa.Controls.NavMenuTests.CanSelectTests;
+
+public partial class TestView2 : UserControl
+{
+    public TestView2()
+    {
+        InitializeComponent();
+        this.DataContext = new TestView2ViewModel();
+    }
+
+    private void NavMenu_OnSelectionChanging(object? sender, SelectionChangingEventArgs e)
+    {
+        if (e.NewItems is [MenuItemViewModel item])
+        {
+            if (item.Text.Contains("2"))
+            {
+                e.CanSelect = false;
+            }
+        }
+    }
+}
+
+public partial class TestView2ViewModel
+{
+    public ObservableCollection<MenuItemViewModel> MenuItems { get; } = new()
+    {
+        new MenuItemViewModel { Text = "Menu Item 1" },
+        new MenuItemViewModel { Text = "Menu Item 2" },
+        new MenuItemViewModel { Text = "Menu Item 3" }
+    };
+}
+
+public partial class MenuItemViewModel: ObservableObject
+{
+    [ObservableProperty] private string? _text;
+}