feat(interactive): host task-based ConPTY sessions in Command Center

Adds an 'Open ConPTY session' entry that fetches a task's launch spec and hosts
an embedded ConPTY terminal as a Mission Control pane, coexisting with the
streamed-log monitor panes (streaming stack untouched). Introduces IMissionControlPane
+ ConPtyPaneViewModel, a non-destructive Panes mirror (Monitors prefix + ConPtySessions
suffix) so unrelated monitor churn never tears down a live terminal, and a grid<->tabs
layout toggle. Launch failures surface via the footer error strip.

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

@@ -0,0 +1,47 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:vm="using:ClaudeDo.Ui.ViewModels.MissionControl"
+             xmlns:views="using:ClaudeDo.Ui.Views"
+             xmlns:loc="using:ClaudeDo.Ui.Localization"
+             xmlns:conv="using:Avalonia.Data.Converters"
+             x:DataType="vm:ConPtyPaneViewModel"
+             x:Class="ClaudeDo.Ui.Views.MissionControl.ConPtyPaneView">
+  <Border Classes="monitor-pane" BorderThickness="1" CornerRadius="10" ClipToBounds="True">
+    <DockPanel LastChildFill="True">
+
+      <!-- Header: title + close -->
+      <Border DockPanel.Dock="Top"
+              Background="{DynamicResource Surface2Brush}"
+              BorderBrush="{DynamicResource LineBrush}"
+              BorderThickness="0,0,0,1" Padding="8,3">
+        <Grid ColumnDefinitions="*,Auto">
+          <TextBlock Grid.Column="0" Classes="meta" Text="{Binding DisplayTitle}"
+                     TextTrimming="CharacterEllipsis"
+                     ToolTip.Tip="{Binding DisplayTitle}"
+                     Foreground="{DynamicResource TextDimBrush}"
+                     VerticalAlignment="Center" Margin="4,0,0,0" />
+          <Button Grid.Column="1" Classes="title-ctrl"
+                  Command="{Binding CloseCommand}"
+                  ToolTip.Tip="{loc:Tr missionControl.closeSession}">
+            <PathIcon Data="{StaticResource Icon.WinClose}" Width="12" Height="12"/>
+          </Button>
+        </Grid>
+      </Border>
+
+      <!-- Start-failure banner -->
+      <Border DockPanel.Dock="Top"
+              IsVisible="{Binding Terminal.StartError, Converter={x:Static conv:ObjectConverters.IsNotNull}}"
+              Background="{DynamicResource ErrorTintBrush}"
+              BorderBrush="{DynamicResource BloodBrush}"
+              BorderThickness="0,0,0,1" Padding="12,6">
+        <TextBlock Classes="meta" Text="{Binding Terminal.StartError}"
+                   Foreground="{DynamicResource BloodBrush}"
+                   TextWrapping="Wrap" />
+      </Border>
+
+      <!-- Embedded ConPTY terminal -->
+      <views:InteractiveTerminalView DataContext="{Binding Terminal}" />
+
+    </DockPanel>
+  </Border>
+</UserControl>