feat(mission-control): Handler-Run per Knopf abbrechen

Ein "Abandon run"-Knopf an Handler-Panes fragt HandlerRoundState.Get(handlerTaskId)
nach den noch offenen (Queued/Running) Tasks des Laufs, bestaetigt mit Anzahl,
cancelt jeden ueber den bestehenden CancelTaskAsync-Pfad und schliesst danach die
Session -- ein Schritt statt Tile schliessen + Queue separat abbrechen. Ohne
offene Tasks (oder ohne Round-Eintrag) schliesst die Aktion direkt, ohne Dialog.
Nur an den beiden Handler-Panes sichtbar (IsListHandler), normale Task-/Ad-hoc-
Panes bleiben unveraendert.

tests/ClaudeDo.Ui.Tests/StubWorkerClient.cs

@@ -138,6 +138,8 @@ public abstract class StubWorkerClient : IWorkerClient
         => Task.FromResult(new LaunchSpec(".", "claude", Array.Empty<string>(), new Dictionary<string, string>()));
     public virtual Task ReportInteractiveSessionExitedAsync(string taskId, int exitCode, CancellationToken ct = default)
         => Task.CompletedTask;
+    public virtual Task<IReadOnlyList<HandlerOpenTaskDto>> GetHandlerOpenTasksAsync(string handlerTaskId, CancellationToken ct = default)
+        => Task.FromResult<IReadOnlyList<HandlerOpenTaskDto>>(Array.Empty<HandlerOpenTaskDto>());
     public virtual Task<LaunchSpec> GetPlanningStartLaunchSpecAsync(string taskId, CancellationToken ct = default)
         => Task.FromResult(new LaunchSpec(".", "claude", Array.Empty<string>(), new Dictionary<string, string>()));
     public virtual Task<LaunchSpec> GetPlanningResumeLaunchSpecAsync(string taskId, CancellationToken ct = default)

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

@@ -966,4 +966,110 @@ public class MissionControlViewModelTests : IDisposable
         vm.ToggleLayoutCommand.Execute(null);
         Assert.False(vm.IsFocusMode);
     }
+
+    // ── Abandon run: single-action "stop session + cancel its still-open tasks" ────────────────
+
+    private sealed class RecordingAbandonWorker : StubWorkerClient
+    {
+        public IReadOnlyList<HandlerOpenTaskDto> OpenTasks { get; set; } = Array.Empty<HandlerOpenTaskDto>();
+        public readonly List<string> Cancelled = new();
+
+        public override Task<IReadOnlyList<HandlerOpenTaskDto>> GetHandlerOpenTasksAsync(string handlerTaskId, CancellationToken ct = default)
+            => Task.FromResult(OpenTasks);
+
+        public override Task CancelTaskAsync(string taskId)
+        {
+            Cancelled.Add(taskId);
+            return Task.CompletedTask;
+        }
+    }
+
+    // A plain OpenConPtySessionAsync pane (not a list handler) never shows/allows the action --
+    // acceptance criterion 5 ("only at handler panes").
+    [Fact]
+    public async Task AbandonRun_OnNonHandlerPane_IsNotAvailable()
+    {
+        var worker = new FakeWorker();
+        using var vm = BuildVm(worker);
+        await vm.OpenConPtySessionAsync("t1");
+        var pane = vm.ConPtySessions[0];
+
+        Assert.False(pane.IsListHandler);
+        Assert.False(pane.AbandonRunCommand.CanExecute(null));
+    }
+
+    [Fact]
+    public async Task AbandonRun_ListHandlerPane_IsListHandlerTrue_CommandAvailable()
+    {
+        var worker = new RecordingAbandonWorker();
+        using var vm = BuildVm(worker);
+        await vm.OpenMergeHelperConPtySessionAsync("L1", new[] { "t1" });
+        var pane = Assert.Single(vm.ConPtySessions);
+
+        Assert.True(pane.IsListHandler);
+        Assert.True(pane.AbandonRunCommand.CanExecute(null));
+    }
+
+    // Acceptance criterion 4: no open tasks (or no round entry, which the fake models the same
+    // way) closes the pane straight away -- no confirmation dialog.
+    [Fact]
+    public async Task AbandonRun_NoOpenTasks_ClosesPaneWithoutConfirming()
+    {
+        var worker = new RecordingAbandonWorker { OpenTasks = Array.Empty<HandlerOpenTaskDto>() };
+        using var vm = BuildVm(worker);
+        await vm.OpenMergeHelperConPtySessionAsync("L1", new[] { "t1" });
+        var pane = Assert.Single(vm.ConPtySessions);
+        var confirmCalled = false;
+        vm.ConfirmAsync = _ => { confirmCalled = true; return Task.FromResult(true); };
+
+        pane.AbandonRunCommand.Execute(null);
+        await Task.Delay(20);
+
+        Assert.False(confirmCalled);
+        Assert.Empty(vm.ConPtySessions);
+    }
+
+    // Acceptance criterion 3 (decline branch): declining leaves the session and its tasks
+    // untouched.
+    [Fact]
+    public async Task AbandonRun_OpenTasks_ConfirmDeclined_LeavesSessionAndTasksUntouched()
+    {
+        var worker = new RecordingAbandonWorker
+        {
+            OpenTasks = new[] { new HandlerOpenTaskDto("t1", "First"), new HandlerOpenTaskDto("t2", "Second") },
+        };
+        using var vm = BuildVm(worker);
+        await vm.OpenMergeHelperConPtySessionAsync("L1", new[] { "t1", "t2" });
+        var pane = Assert.Single(vm.ConPtySessions);
+        string? confirmMessage = null;
+        vm.ConfirmAsync = msg => { confirmMessage = msg; return Task.FromResult(false); };
+
+        pane.AbandonRunCommand.Execute(null);
+        await Task.Delay(20);
+
+        Assert.NotNull(confirmMessage);
+        Assert.Empty(worker.Cancelled);
+        Assert.Single(vm.ConPtySessions);
+    }
+
+    // Acceptance criteria 1-3 (accept branch): the count is confirmed, every open task is
+    // cancelled, then the pane closes -- one action instead of two.
+    [Fact]
+    public async Task AbandonRun_OpenTasks_ConfirmAccepted_CancelsEachThenClosesPane()
+    {
+        var worker = new RecordingAbandonWorker
+        {
+            OpenTasks = new[] { new HandlerOpenTaskDto("t1", "First"), new HandlerOpenTaskDto("t2", "Second") },
+        };
+        using var vm = BuildVm(worker);
+        await vm.OpenMergeHelperConPtySessionAsync("L1", new[] { "t1", "t2" });
+        var pane = Assert.Single(vm.ConPtySessions);
+        vm.ConfirmAsync = _ => Task.FromResult(true);
+
+        pane.AbandonRunCommand.Execute(null);
+        await Task.Delay(20);
+
+        Assert.Equal(new[] { "t1", "t2" }, worker.Cancelled);
+        Assert.Empty(vm.ConPtySessions);
+    }
 }