fix(claude-do): Maximize button hides the window instead of maximizing

## Bug
Clicking the maximize control in the custom title bar makes the main window disappear/hide instead of filling the screen. Restore is then hard or impossible.

## Where
`MainWindow` uses custom client-area chrome, so the OS does not manage maximize:
- `src/ClaudeDo.Ui/Views/MainWindow.axaml:14-16` — `WindowDecorations="BorderOnly"`, `ExtendClientAreaToDecorationsHint="True"`, `ExtendClientAr

ClaudeDo-Task: 7d3d9501a8eb4111b9d433fd917f5a22

src/ClaudeDo.Ui/Views/MainWindow.axaml

@@ -22,7 +22,7 @@
     <KeyBinding Gesture="Shift+OemQuestion" Command="{Binding FocusSearchCommand}"/>
     <KeyBinding Gesture="Ctrl+N" Command="{Binding FocusAddTaskCommand}"/>
   </Window.KeyBindings>
-  <Grid RowDefinitions="36,Auto,*,22">
+  <Grid x:Name="RootGrid" RowDefinitions="36,Auto,*,22">
     <!-- Custom title bar -->
     <Border Grid.Row="0"
             Background="{DynamicResource DeepBrush}"

src/ClaudeDo.Ui/Views/MainWindow.axaml.cs

@@ -27,6 +27,8 @@ public partial class MainWindow : Window
         base.OnPropertyChanged(change);
         if (change.Property == WindowStateProperty)
             UpdateMaxIcon();
+        if (change.Property == OffScreenMarginProperty)
+            RootGrid.Margin = OffScreenMargin;
     }
 
     private void UpdateMaxIcon()