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>

Window/X11Window.cs

@@ -288,8 +288,12 @@ public class X11Window : IDisposable
 
         KeyDown?.Invoke(this, new KeyEventArgs(key, modifiers));
 
-        // Generate text input for printable characters
-        if (keysym >= 32 && keysym <= 126)
+        // Generate text input for printable characters, but NOT when Control or Alt is held
+        // (those are keyboard shortcuts, not text input)
+        bool isControlHeld = (keyEvent.State & 0x04) != 0; // ControlMask
+        bool isAltHeld = (keyEvent.State & 0x08) != 0;     // Mod1Mask (Alt)
+
+        if (keysym >= 32 && keysym <= 126 && !isControlHeld && !isAltHeld)
         {
             TextInput?.Invoke(this, new TextInputEventArgs(((char)keysym).ToString()));
         }