Preview 3: Complete control implementation with XAML data binding

Major milestone adding full control functionality:

Controls Enhanced:
- Entry/Editor: Full keyboard input, cursor navigation, selection, clipboard
- CollectionView: Data binding, selection highlighting, scrolling
- CheckBox/Switch/Slider: Interactive state management
- Picker/DatePicker/TimePicker: Dropdown selection with popup overlays
- ProgressBar/ActivityIndicator: Animated progress display
- Button: Press/release visual states
- Border/Frame: Rounded corners, stroke styling
- Label: Text wrapping, alignment, decorations
- Grid/StackLayout: Margin and padding support

Features Added:
- DisplayAlert dialogs with button actions
- NavigationPage with toolbar and back navigation
- Shell with flyout menu navigation
- XAML value converters for data binding
- Margin support in all layout containers
- Popup overlay system for pickers

New Samples:
- TodoApp: Full CRUD task manager with NavigationPage
- ShellDemo: Comprehensive control showcase

Removed:
- ControlGallery (replaced by ShellDemo)
- LinuxDemo (replaced by TodoApp)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Handlers/ButtonHandler.cs

@@ -20,6 +20,7 @@ public partial class ButtonHandler : ViewHandler<IButton, SkiaButton>
         [nameof(IButtonStroke.CornerRadius)] = MapCornerRadius,
         [nameof(IView.Background)] = MapBackground,
         [nameof(IPadding.Padding)] = MapPadding,
+        [nameof(IView.IsEnabled)] = MapIsEnabled,
     };
 
     public static CommandMapper<IButton, ButtonHandler> CommandMapper = new(ViewHandler.ViewCommandMapper)
@@ -47,6 +48,18 @@ public partial class ButtonHandler : ViewHandler<IButton, SkiaButton>
         platformView.Clicked += OnClicked;
         platformView.Pressed += OnPressed;
         platformView.Released += OnReleased;
+
+        // Manually map all properties on connect since MAUI may not trigger updates
+        // for properties that were set before handler connection
+        if (VirtualView != null)
+        {
+            MapStrokeColor(this, VirtualView);
+            MapStrokeThickness(this, VirtualView);
+            MapCornerRadius(this, VirtualView);
+            MapBackground(this, VirtualView);
+            MapPadding(this, VirtualView);
+            MapIsEnabled(this, VirtualView);
+        }
     }
 
     protected override void DisconnectHandler(SkiaButton platformView)
@@ -88,7 +101,8 @@ public partial class ButtonHandler : ViewHandler<IButton, SkiaButton>
 
         if (button.Background is SolidPaint solidPaint && solidPaint.Color is not null)
         {
-            handler.PlatformView.BackgroundColor = solidPaint.Color.ToSKColor();
+            // Set ButtonBackgroundColor (used for rendering) not base BackgroundColor
+            handler.PlatformView.ButtonBackgroundColor = solidPaint.Color.ToSKColor();
         }
     }
 
@@ -103,6 +117,14 @@ public partial class ButtonHandler : ViewHandler<IButton, SkiaButton>
             (float)padding.Right,
             (float)padding.Bottom);
     }
+
+    public static void MapIsEnabled(ButtonHandler handler, IButton button)
+    {
+        if (handler.PlatformView is null) return;
+        Console.WriteLine($"[ButtonHandler] MapIsEnabled - Text='{handler.PlatformView.Text}', IsEnabled={button.IsEnabled}");
+        handler.PlatformView.IsEnabled = button.IsEnabled;
+        handler.PlatformView.Invalidate();
+    }
 }
 
 /// <summary>
@@ -124,6 +146,21 @@ public partial class TextButtonHandler : ButtonHandler
     {
     }
 
+    protected override void ConnectHandler(SkiaButton platformView)
+    {
+        base.ConnectHandler(platformView);
+
+        // Manually map text properties on connect since MAUI may not trigger updates
+        // for properties that were set before handler connection
+        if (VirtualView is ITextButton textButton)
+        {
+            MapText(this, textButton);
+            MapTextColor(this, textButton);
+            MapFont(this, textButton);
+            MapCharacterSpacing(this, textButton);
+        }
+    }
+
     public static void MapText(TextButtonHandler handler, ITextButton button)
     {
         if (handler.PlatformView is null) return;