chore(ui): remove dead Mission Control monitor-pane stack

Auto-seeding of monitor tiles was disabled in 724814f; Mission Control now
only shows ConPTY panes. Removes Monitors/EnsureMonitor/SeedActive, the
detach/re-dock machinery, MonitorPaneView and the detached monitor window,
plus their tests and orphaned localization keys.

TaskMonitorViewModel itself stays: DetailsIslandViewModel still uses it as
the backing state for the task Log/AgentState/AskUser-question UI, so only
its Mission-Control-only members (Title/DisplayTitle, detach, cancel command,
IMissionControlPane) were stripped. IMissionControlPane/Panes were kept
(now a 1:1 mirror of ConPtySessions) rather than dissolved, to avoid
churning the still-live ConPTY pane tests and AXAML for a single-implementer
interface.

Visual verification still open: Mission Control with several open ConPTY
tiles, and the Focus/Overview toggle.

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

@@ -1,24 +1,17 @@
 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:vm="using:ClaudeDo.Ui.ViewModels"
-             xmlns:vmi="using:ClaudeDo.Ui.ViewModels.Islands"
              xmlns:vmm="using:ClaudeDo.Ui.ViewModels.MissionControl"
              xmlns:mc="using:ClaudeDo.Ui.Views.MissionControl"
              xmlns:loc="using:ClaudeDo.Ui.Localization"
              x:DataType="vm:MissionControlViewModel"
              x:Class="ClaudeDo.Ui.Views.MissionControl.MissionControlView">
   <UserControl.DataTemplates>
-    <!-- Polymorphic pane templates: both the grid ItemsControl and the focus-mode TabControl
-         resolve per-item content through these (no explicit ItemTemplate on either). -->
-    <DataTemplate DataType="vmi:TaskMonitorViewModel">
-      <mc:MonitorPaneView Margin="6" />
-    </DataTemplate>
     <DataTemplate DataType="vmm:ConPtyPaneViewModel">
       <mc:ConPtyPaneView Margin="6" />
     </DataTemplate>
   </UserControl.DataTemplates>
-  <DockPanel LastChildFill="True" Background="{DynamicResource VoidBrush}"
-             DragDrop.AllowDrop="True">
+  <DockPanel LastChildFill="True" Background="{DynamicResource VoidBrush}">
 
     <!-- Header -->
     <Border DockPanel.Dock="Top"
@@ -50,9 +43,6 @@
             <PathIcon Data="{StaticResource Icon.Settings}" Width="15" Height="15"
                       Foreground="{DynamicResource TextMuteBrush}"/>
           </Button>
-          <Button Classes="btn"
-                  Content="{loc:Tr missionControl.clearFinished}"
-                  Command="{Binding ClearFinishedCommand}" />
         </StackPanel>
       </Grid>
     </Border>