fix: resolve CI annotations by allowing nullable UIElement properties on Border

- Allowed nulls on `Border.Title` and `Border.StatusBar` to eliminate compiler warnings about missing `required` modifier.

Co-authored-by: tedd <493224+tedd@users.noreply.github.com>

Author: google-labs-jules[bot]

src/Tedd.TUI.Tests/ItemsControlTests.cs

@@ -14,7 +14,7 @@ private class TestItemsControl : ItemsControl
     public void ItemsSource_Populates_Items()
     {
         var control = new TestItemsControl();
-        string[] source = [ "A", "B", "C" ];
+        string[] source = ["A", "B", "C"];
 
         control.ItemsSource = source;
 
@@ -111,7 +111,7 @@ public void ItemsSource_Move_Updates_Items()
     public void Items_IsReadOnly_When_ItemsSource_Set()
     {
         var control = new TestItemsControl();
-        control.ItemsSource = (string[])[ "A" ];
+        control.ItemsSource = (string[])["A"];
 
         Assert.Throws<InvalidOperationException>(() => control.Items.Add("B"));
         Assert.Throws<InvalidOperationException>(() => control.Items.RemoveAt(0));
@@ -214,7 +214,7 @@ public void ItemTemplate_Change_Repopulates_ItemsPresenter()
     {
         var control = new TestItemsControl();
 
-        TestItem[] items = [ new TestItem { Name = "A" }, new TestItem { Name = "B" } ];
+        TestItem[] items = [new TestItem { Name = "A" }, new TestItem { Name = "B" }];
         control.ItemsSource = items;
 
         control.Template = new ControlTemplate(parent =>

src/Tedd.TUI.Tests/MarkdownViewTests.cs

@@ -184,7 +184,7 @@ public void MarkdownView_TablePreservesEmptyCells()
         var table = (Table)doc.GetVisualChild(0);
 
         // Row count check
-        Assert.Equal(1, table.Rows.Count);
+        Assert.Single(table.Rows);
         var row = table.Rows[0];
         Assert.Equal(3, row.Cells.Count);
     }
@@ -204,7 +204,7 @@ public void MarkdownView_TablePadsShortRowsToColumnCount()
         var table = (Table)doc.GetVisualChild(0);
 
         Assert.Equal(4, table.Columns.Count);
-        Assert.Equal(1, table.Rows.Count);
+        Assert.Single(table.Rows);
         Assert.Equal(4, table.Rows[0].Cells.Count);
     }
 

src/Tedd.TUI.Tests/ValidatorGroupBoxTests.cs

@@ -115,15 +115,17 @@ public void BoundaryAndEdgeVerification_NegativeConstraints()
         var groupBox = new GroupBox { BoxStyle = BoxStyle.Single, Header = "Neg" };
         stack.Children.Add(groupBox);
 
-        var ex = Record.Exception(() => {
+        var ex = Record.Exception(() =>
+        {
             stack.Measure(new Size(-10, -10));
             stack.Arrange(new Rect(0, 0, -10, -10));
         });
 
         Assert.Null(ex); // Layout should not crash on negative dimensions
 
         var buffer = new VirtualBuffer(10, 10);
-        var ex2 = Record.Exception(() => {
+        var ex2 = Record.Exception(() =>
+        {
             stack.Render(buffer, 0, 0);
         });
 

src/Tedd.TUI.Tests/ValidatorLayoutMatrixTests.cs

@@ -331,15 +331,17 @@ public void BoundaryAndEdgeVerification_NegativeConstraints()
 
         // Negative size should be handled gracefully without exception
         // The Measure/Arrange algorithms typically clamp sizes to 0
-        var ex = Record.Exception(() => {
+        var ex = Record.Exception(() =>
+        {
             stack.Measure(new Size(-10, -10));
             stack.Arrange(new Rect(0, 0, -10, -10));
         });
 
         Assert.Null(ex); // Layout should not crash on negative dimensions
 
         var buffer = new VirtualBuffer(10, 10);
-        var ex2 = Record.Exception(() => {
+        var ex2 = Record.Exception(() =>
+        {
             stack.Render(buffer, 0, 0);
         });
 

src/Tedd.TUI/Border.cs

@@ -11,7 +11,7 @@ public UIElement Child
         set => Content = value;
     }
 
-    public UIElement Title
+    public UIElement? Title
     {
         get;
         set
@@ -39,7 +39,7 @@ public HorizontalAlignment TitleAlignment
         }
     } = HorizontalAlignment.Left;
 
-    public UIElement StatusBar
+    public UIElement? StatusBar
     {
         get;
         set