feat(ui): drag-reorder Mission Control panes by their header

src/ClaudeDo.Ui/Views/MissionControl/MonitorPaneView.axaml

@@ -6,6 +6,7 @@
              x:DataType="vm:TaskMonitorViewModel"
              x:Class="ClaudeDo.Ui.Views.MissionControl.MonitorPaneView">
   <Border Classes="monitor-pane"
+          DragDrop.AllowDrop="True"
           Classes.mon-review="{Binding IsWaitingForReview}"
           Classes.mon-done="{Binding IsDone}"
           Classes.mon-roadblock="{Binding HasRoadblock}"
@@ -17,7 +18,8 @@
       <Border DockPanel.Dock="Top"
               Background="{DynamicResource Surface2Brush}"
               BorderBrush="{DynamicResource LineBrush}"
-              BorderThickness="0,0,0,1" Padding="6,3">
+              BorderThickness="0,0,0,1" Padding="6,3"
+              PointerPressed="OnHeaderPressed">
         <StackPanel Orientation="Horizontal" Spacing="2"
                     HorizontalAlignment="Right" VerticalAlignment="Center">
           <Button Classes="title-ctrl"