feat(worker): report worktree-creation phase on OperationProgress

Fills the silent gap between Queued and the first agent output: WorktreeManager
now broadcasts a "creating_worktree" phase (before the initial git worktree add
and again for the self-heal retry section) through the existing OperationProgress
channel, and the task row shows it via the pre-existing but unused
ops.worker.creatingWorktree locale key until the next entity refresh clears it.

Confirmed the 2026-08-07 triage finding still holds: TaskRunner already
broadcasts WorktreeUpdated right after WorktreeManager.CreateAsync
(TaskRunner.cs:342-346, :501) -- no second broadcast added there.

src/ClaudeDo.Ui/ViewModels/Islands/TasksIslandViewModel.cs

@@ -188,6 +188,7 @@ public sealed partial class TasksIslandViewModel : ViewModelBase, IDisposable
             _worker.ConnectionRestoredEvent += () => LoadForList(_currentList);
             _worker.RefineStartedEvent     += OnRefineStarted;
             _worker.RefineFinishedEvent    += OnRefineFinished;
+            _worker.OperationProgressEvent += OnWorkerOperationProgress;
         }
         _langChangedHandler = (_, _) => RefreshLocalizedText();
         Loc.LanguageChanged += _langChangedHandler;
@@ -1563,6 +1564,18 @@ public sealed partial class TasksIslandViewModel : ViewModelBase, IDisposable
         if (row is not null) row.IsRefining = false;
     }
 
+    // OperationProgress is a generic channel shared with merge phases (TaskMergeService), whose
+    // opKey is also the task id — filter on the phase token so a merge in flight can't clobber
+    // this row's creation-phase banner.
+    private const string CreationPhaseCreatingWorktree = "creating_worktree";
+
+    private void OnWorkerOperationProgress(string opKey, string phase, int current, int total)
+    {
+        if (phase != CreationPhaseCreatingWorktree) return;
+        var row = Items.FirstOrDefault(r => r.Id == opKey);
+        if (row is not null) row.CreationPhase = phase;
+    }
+
     partial void OnSelectedTaskChanged(TaskRowViewModel? value)
     {
         foreach (var i in Items) i.IsSelected = ReferenceEquals(i, value);