fix(merge): conventional merge-commit default and live verify progress

The merge commit message was hand-rolled per caller ("Merge task: <title>",
"Merge <branch>", "Merge subtask") and ignored the task's commit type. Every
caller now passes a blank message and TaskMergeService fills in
CommitMessageBuilder.BuildMerge -> {commitType}(list-slug): merge <title> plus the
ClaudeDo-Task trailer; the merge modal prefills it from GetMergeTargets.

A merge whose list has a verify command holds the MergeTask call for minutes (5m46s
on this repo), during which the modal only disabled its button - no spinner, no
message, so a landed merge looked like a dead app. TaskMergeService now broadcasts
MergeProgress(taskId, phase, elapsedSeconds) for the merging and verifying phases
(re-reported every 30s) plus a WorkerLog line when verify starts; the modal shows a
spinner and the localized phase.

src/ClaudeDo.Ui/Services/Interfaces/IWorkerClient.cs

@@ -34,6 +34,11 @@ public interface IWorkerClient : INotifyPropertyChanged
     event Action<string>? PrepLineEvent;
     event Action<bool>? PrepFinishedEvent;
 
+    /// <summary>(taskId, phase, elapsedSeconds) — phase of an in-flight single-task merge
+    /// ("merging" | "verifying"). Fires while the MergeTask call itself is still pending, so the
+    /// waiting UI can show what it's blocked on; the verify phase re-fires every 30 s.</summary>
+    event Action<string, string, int>? MergeProgressEvent;
+
     event Action<string, string>? PlanningMergeStartedEvent;
     event Action<string, string>? PlanningSubtaskMergedEvent;
     /// <summary>(planningTaskId, subtaskId, conflictedFiles, externallyDriven). externallyDriven

src/ClaudeDo.Ui/Services/WorkerClient.cs

@@ -64,6 +64,8 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
 
     public event Action<UsageSnapshotDto>? UsageUpdatedEvent;
 
+    public event Action<string, string, int>? MergeProgressEvent;
+
     public event Action<string, string>? PlanningMergeStartedEvent;
     public event Action<string, string>? PlanningSubtaskMergedEvent;
     public event Action<string, string, IReadOnlyList<string>, bool>? PlanningMergeConflictEvent;
@@ -172,6 +174,11 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
                 WorkerLogReceivedEvent?.Invoke(new WorkerLogEntry(message, level, timestampUtc)));
         });
 
+        _hub.On<string, string, int>("MergeProgress", (taskId, phase, elapsedSeconds) =>
+        {
+            Dispatcher.UIThread.Post(() => MergeProgressEvent?.Invoke(taskId, phase, elapsedSeconds));
+        });
+
         _hub.On<string, string>("PlanningMergeStarted", (planningTaskId, targetBranch) =>
         {
             Dispatcher.UIThread.Post(() => PlanningMergeStartedEvent?.Invoke(planningTaskId, targetBranch));
@@ -694,7 +701,8 @@ public record MergeResultDto(string Status, IReadOnlyList<string> ConflictFiles,
 public record BaseDirtyWarningDto(int ModifiedCount, int UntrackedCount);
 public record SetTaskStatusResultDto(BaseDirtyWarningDto? BaseDirty);
 public record MergePreviewDto(string Status, IReadOnlyList<string> ConflictFiles, int ChangedFileCount);
-public record MergeTargetsDto(string DefaultBranch, IReadOnlyList<string> LocalBranches);
+public record MergeTargetsDto(
+    string DefaultBranch, IReadOnlyList<string> LocalBranches, string DefaultCommitMessage);
 public record MergeConflictDocumentsDto(string TaskId, IReadOnlyList<ConflictDocumentDto> Files);
 public record ConflictDocumentDto(string Path, bool IsBinary, IReadOnlyList<MergeSegmentDto> Segments);
 public record MergeSegmentDto(bool IsConflict, string Text, string Ours, string? Base, string Theirs);

src/ClaudeDo.Ui/ViewModels/Modals/MergeModalViewModel.cs

@@ -21,6 +21,12 @@ public sealed partial class MergeModalViewModel : ViewModelBase
     [ObservableProperty] private string _commitMessage = "";
 
     [ObservableProperty][NotifyCanExecuteChangedFor(nameof(SubmitCommand))] private bool _isBusy;
+
+    /// What the pending merge is doing right now, fed by the worker's MergeProgress broadcast.
+    /// A merge whose list has a verify command can occupy this call for minutes — without this the
+    /// modal only greys the button out and looks dead.
+    [ObservableProperty] private string? _progressMessage;
+
     [ObservableProperty] private string? _errorMessage;
     [ObservableProperty] private string? _warningMessage;
     [ObservableProperty] private string? _successMessage;
@@ -58,6 +64,10 @@ public sealed partial class MergeModalViewModel : ViewModelBase
                 ErrorMessage = Loc.T("vm.merge.workerOfflineBranches");
                 return;
             }
+            // The worker owns the default message — only it knows the task's commit type and the
+            // list name the scope is slugged from. The locale string stays as the offline fallback.
+            if (!string.IsNullOrWhiteSpace(targets.DefaultCommitMessage))
+                CommitMessage = targets.DefaultCommitMessage;
             foreach (var b in targets.LocalBranches) Branches.Add(b);
             SelectedBranch = Branches.Contains(targets.DefaultBranch)
                 ? targets.DefaultBranch
@@ -81,6 +91,10 @@ public sealed partial class MergeModalViewModel : ViewModelBase
         ErrorMessage = null;
         WarningMessage = null;
         SuccessMessage = null;
+        // Subscribed only for the duration of the call: the worker's broadcast reaches every
+        // client, and a transient VM left on that event would outlive its window.
+        ProgressMessage = Loc.T("vm.merge.progressMerging");
+        _worker.MergeProgressEvent += OnMergeProgress;
         try
         {
             var result = await _worker.MergeTaskAsync(
@@ -133,10 +147,28 @@ public sealed partial class MergeModalViewModel : ViewModelBase
         }
         finally
         {
+            _worker.MergeProgressEvent -= OnMergeProgress;
+            ProgressMessage = null;
             IsBusy = false;
         }
     }
 
+    private void OnMergeProgress(string taskId, string phase, int elapsedSeconds)
+    {
+        if (taskId != TaskId) return;
+        ProgressMessage = phase switch
+        {
+            MergePhaseVerifying => Loc.T("vm.merge.progressVerifying", FormatElapsed(elapsedSeconds)),
+            _ => Loc.T("vm.merge.progressMerging"),
+        };
+    }
+
+    /// Mirrors TaskMergeService.PhaseVerifying — a hub payload token, not a display string.
+    private const string MergePhaseVerifying = "verifying";
+
+    private static string FormatElapsed(int seconds) =>
+        TimeSpan.FromSeconds(Math.Max(0, seconds)).ToString(@"mm\:ss");
+
     [RelayCommand]
     private void Cancel() => CloseAction?.Invoke();
 }

src/ClaudeDo.Ui/ViewModels/Modals/WorktreesOverviewModalViewModel.cs

@@ -440,8 +440,8 @@ public sealed partial class WorktreesOverviewModalViewModel : ViewModelBase
                 MergeResultDto result;
                 try
                 {
-                    result = await mergeFn(row.TaskId, target!, false,
-                        Loc.T("vm.merge.commitMessage", row.TaskTitle));
+                    // Blank message: the worker builds the conventional default per task.
+                    result = await mergeFn(row.TaskId, target!, false, "");
                 }
                 catch
                 {

src/ClaudeDo.Ui/Views/Modals/MergeModalView.axaml

@@ -22,6 +22,15 @@
     <ctl:ModalShell.Footer>
       <StackPanel Orientation="Horizontal" Spacing="8"
                   HorizontalAlignment="Right" VerticalAlignment="Center">
+        <!-- A merge into a list with a verify command holds this dialog for minutes; without a
+             live phase here the disabled button is the only feedback and reads as a dead app. -->
+        <StackPanel Orientation="Horizontal" Spacing="8" VerticalAlignment="Center"
+                    IsVisible="{Binding IsBusy}">
+          <Ellipse Classes="spinner" VerticalAlignment="Center"/>
+          <TextBlock Classes="meta" VerticalAlignment="Center"
+                     Text="{Binding ProgressMessage}"
+                     IsVisible="{Binding ProgressMessage, Converter={x:Static ObjectConverters.IsNotNull}}"/>
+        </StackPanel>
         <Button Classes="btn" Content="{loc:Tr modals.merge.cancel}" Command="{Binding CancelCommand}" MinWidth="90"/>
         <Button Content="{loc:Tr modals.merge.merge}" Classes="primary"
                 Command="{Binding SubmitCommand}"