feat(interactive): New session button for ad-hoc ConPTY sessions

Adds a 'New session' header button in Mission Control that opens a folder picker
and starts a task-less embedded ConPTY session in the chosen directory. ConPtyPaneViewModel
TaskId is now nullable (ad-hoc panes have no task and are never deduped) with a
CreateAdHoc factory; the view does the picking, the VM stays picker-agnostic.

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

@@ -7,14 +7,15 @@ 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
+/// Command Center pane hosting an embedded ConPTY terminal for either one task's interactive
+/// Claude session, or an ad-hoc/free session in a user-chosen directory (no task, <see cref="TaskId"/>
+/// is null — ad-hoc panes are never deduped, unlike task-based ones). 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; }
+    public string? TaskId { get; }
 
     [ObservableProperty] private string _displayTitle;
 
@@ -26,7 +27,9 @@ public sealed partial class ConPtyPaneViewModel : ViewModelBase, IMissionControl
     /// <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)
+    /// <summary>Task-based pane — dedup'd by <see cref="TaskId"/>. Pass null for an ad-hoc pane
+    /// (no task, never deduped); prefer <see cref="CreateAdHoc"/> at ad-hoc call sites.</summary>
+    public ConPtyPaneViewModel(string? taskId, string displayTitle, TerminalLaunchDescriptor descriptor)
     {
         TaskId = taskId;
         _displayTitle = displayTitle;
@@ -34,6 +37,10 @@ public sealed partial class ConPtyPaneViewModel : ViewModelBase, IMissionControl
         Terminal.Start(descriptor);
     }
 
+    /// <summary>Ad-hoc pane — no task, no dedup.</summary>
+    public static ConPtyPaneViewModel CreateAdHoc(string displayTitle, TerminalLaunchDescriptor descriptor)
+        => new(null, displayTitle, descriptor);
+
     private void OnTerminalPropertyChanged(object? sender, PropertyChangedEventArgs e)
     {
         if (e.PropertyName == nameof(InteractiveTerminalViewModel.StartError) && Terminal.StartError is { Length: > 0 } error)

src/ClaudeDo.Ui/ViewModels/MissionControlViewModel.cs

@@ -1,5 +1,6 @@
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
+using System.IO;
 using System.Linq;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
@@ -265,6 +266,30 @@ public sealed partial class MissionControlViewModel : ViewModelBase, IDisposable
         }
     }
 
+    // Ad-hoc (task-less) ConPTY session in a user-chosen directory. Never deduped — every call
+    // opens a fresh pane, unlike the task-based OpenConPtySessionAsync above.
+    public async System.Threading.Tasks.Task OpenAdHocConPtySessionAsync(string directory)
+    {
+        if (string.IsNullOrEmpty(directory)) return;
+
+        var title = Path.GetFileName(directory.TrimEnd('\\', '/'));
+        if (string.IsNullOrEmpty(title)) title = directory;
+
+        try
+        {
+            var spec = await _worker.GetAdHocLaunchSpecAsync(directory);
+            var descriptor = new TerminalLaunchDescriptor(spec.Cwd, spec.Exe, spec.Args, spec.Env);
+            var pane = ConPtyPaneViewModel.CreateAdHoc(title, descriptor);
+            pane.ErrorReported += OnConPtyPaneError;
+            pane.CloseRequested += CloseConPtySession;
+            ConPtySessions.Add(pane);
+        }
+        catch (Exception ex)
+        {
+            ErrorReported?.Invoke(Loc.T("missionControl.conptyLaunchFailed", ex.Message));
+        }
+    }
+
     private void OnConPtyPaneError(string message) => ErrorReported?.Invoke(message);
 
     private void CloseConPtySession(ConPtyPaneViewModel pane)