Show 'Unsupported' in config dialog for monitors without input options

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

DellMonitorControl/ConfigWindow.xaml.cs

@@ -34,6 +34,22 @@ public partial class ConfigWindow : Window
         spPorts.Children.Clear();
         _portRows.Clear();
 
+        // Show unsupported message if no ports available
+        if (_availablePorts == null || _availablePorts.Count == 0)
+        {
+            spPorts.Children.Add(new TextBlock
+            {
+                Text = "Unsupported",
+                Foreground = Brushes.Gray,
+                FontSize = 16,
+                FontStyle = FontStyles.Italic,
+                HorizontalAlignment = HorizontalAlignment.Center,
+                VerticalAlignment = VerticalAlignment.Center,
+                Margin = new Thickness(0, 40, 0, 40)
+            });
+            return;
+        }
+
         foreach (var port in _availablePorts)
         {
             var existingPortConfig = config.Ports.FirstOrDefault(p => p.VcpValue == port.Value);