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/ViewModels/MissionControl/ConPtyPaneViewModel.cs

@@ -0,0 +1,52 @@
+using System;
+using System.ComponentModel;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using ClaudeDo.Ui.Services;
+
+namespace ClaudeDo.Ui.ViewModels.MissionControl;
+
+/// <summary>
+/// Command Center pane hosting an embedded ConPTY terminal for one task's interactive Claude
+/// session (task-based only — no ad-hoc/free sessions yet). Distinct from the streamed-log
+/// <see cref="ClaudeDo.Ui.ViewModels.Islands.TaskMonitorViewModel"/> pane; the two coexist until
+/// the streaming interactive stack is removed.
+/// </summary>
+public sealed partial class ConPtyPaneViewModel : ViewModelBase, IMissionControlPane, IDisposable
+{
+    public string TaskId { get; }
+
+    [ObservableProperty] private string _displayTitle;
+
+    public InteractiveTerminalViewModel Terminal { get; } = new();
+
+    /// <summary>Raised when the terminal failed to start — the host surfaces this via the footer error strip.</summary>
+    public event Action<string>? ErrorReported;
+
+    /// <summary>Set by the host (Mission Control) to remove this pane from its collection.</summary>
+    public Action<ConPtyPaneViewModel>? CloseRequested { get; set; }
+
+    public ConPtyPaneViewModel(string taskId, string displayTitle, TerminalLaunchDescriptor descriptor)
+    {
+        TaskId = taskId;
+        _displayTitle = displayTitle;
+        Terminal.PropertyChanged += OnTerminalPropertyChanged;
+        Terminal.Start(descriptor);
+    }
+
+    private void OnTerminalPropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (e.PropertyName == nameof(InteractiveTerminalViewModel.StartError) && Terminal.StartError is { Length: > 0 } error)
+            ErrorReported?.Invoke(error);
+    }
+
+    [RelayCommand]
+    private void Close() => CloseRequested?.Invoke(this);
+
+    public void Dispose()
+    {
+        Terminal.PropertyChanged -= OnTerminalPropertyChanged;
+        Terminal.Kill();
+        Terminal.Dispose();
+    }
+}

src/ClaudeDo.Ui/ViewModels/MissionControl/IMissionControlPane.cs

@@ -0,0 +1,12 @@
+namespace ClaudeDo.Ui.ViewModels.MissionControl;
+
+/// <summary>
+/// Common contract for anything hosted as a pane in the Command Center — implemented by both
+/// the streamed-log <see cref="ClaudeDo.Ui.ViewModels.Islands.TaskMonitorViewModel"/> and the
+/// embedded ConPTY <see cref="ConPtyPaneViewModel"/> — so the layout toggle (grid/tabs) can
+/// bind one heterogeneous pane collection.
+/// </summary>
+public interface IMissionControlPane
+{
+    string DisplayTitle { get; }
+}