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.

tests/ClaudeDo.Ui.Tests/ViewModels/MissionControlViewModelTests.cs

@@ -4,6 +4,7 @@ using ClaudeDo.Data.Models;
 using ClaudeDo.Ui.Services;
 using ClaudeDo.Ui.ViewModels;
 using ClaudeDo.Ui.ViewModels.Islands;
+using ClaudeDo.Ui.ViewModels.MissionControl;
 using Microsoft.EntityFrameworkCore;
 using Xunit;
 using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
@@ -262,4 +263,94 @@ public class MissionControlViewModelTests : IDisposable
         var entity = await verify.Tasks.FirstAsync(t => t.Id == "idleTask");
         Assert.Equal(TaskStatus.Queued, entity.Status);
     }
+
+    private sealed class ThrowingLaunchSpecWorker : StubWorkerClient
+    {
+        public override Task<LaunchSpec> GetInteractiveLaunchSpecAsync(string taskId, CancellationToken ct = default)
+            => throw new InvalidOperationException("no worktree");
+    }
+
+    [Fact]
+    public async Task OpenConPtySessionAsync_AddsPane_ToConPtySessionsAndPanes()
+    {
+        var worker = new FakeWorker();
+        using var vm = BuildVm(worker);
+
+        await vm.OpenConPtySessionAsync("t1");
+
+        Assert.Single(vm.ConPtySessions);
+        Assert.Equal("t1", vm.ConPtySessions[0].TaskId);
+        Assert.Single(vm.Panes);
+        Assert.Same(vm.ConPtySessions[0], vm.Panes[0]);
+        Assert.True(vm.HasPanes);
+    }
+
+    [Fact]
+    public async Task OpenConPtySessionAsync_SameTaskTwice_DoesNotDuplicate()
+    {
+        var worker = new FakeWorker();
+        using var vm = BuildVm(worker);
+
+        await vm.OpenConPtySessionAsync("t1");
+        await vm.OpenConPtySessionAsync("t1");
+
+        Assert.Single(vm.ConPtySessions);
+    }
+
+    [Fact]
+    public async Task OpenConPtySessionAsync_WorkerThrows_RaisesErrorReported_NoPaneAdded()
+    {
+        var worker = new ThrowingLaunchSpecWorker();
+        using var vm = BuildVm(worker);
+        string? error = null;
+        vm.ErrorReported += msg => error = msg;
+
+        await vm.OpenConPtySessionAsync("t1");
+
+        Assert.Empty(vm.ConPtySessions);
+        Assert.Empty(vm.Panes);
+        Assert.NotNull(error);
+    }
+
+    [Fact]
+    public async Task Panes_CombinesMonitorsThenConPtySessions_InOrder()
+    {
+        var worker = new FakeWorker();
+        using var vm = BuildVm(worker);
+
+        worker.RaiseTaskStarted("slot-1", "t1", DateTime.UtcNow);
+        await vm.OpenConPtySessionAsync("t2");
+
+        Assert.Equal(2, vm.Panes.Count);
+        Assert.IsType<TaskMonitorViewModel>(vm.Panes[0]);
+        Assert.IsType<ConPtyPaneViewModel>(vm.Panes[1]);
+        Assert.Equal(2, vm.ColumnCount);
+    }
+
+    [Fact]
+    public async Task CloseConPtySession_RemovesFromConPtySessionsAndPanes()
+    {
+        var worker = new FakeWorker();
+        using var vm = BuildVm(worker);
+        await vm.OpenConPtySessionAsync("t1");
+        var pane = vm.ConPtySessions[0];
+
+        pane.CloseCommand.Execute(null);
+
+        Assert.Empty(vm.ConPtySessions);
+        Assert.Empty(vm.Panes);
+    }
+
+    [Fact]
+    public void ToggleLayoutCommand_FlipsIsFocusMode()
+    {
+        var worker = new FakeWorker();
+        using var vm = BuildVm(worker);
+
+        Assert.False(vm.IsFocusMode);
+        vm.ToggleLayoutCommand.Execute(null);
+        Assert.True(vm.IsFocusMode);
+        vm.ToggleLayoutCommand.Execute(null);
+        Assert.False(vm.IsFocusMode);
+    }
 }