feat(ui): separate OperationStatus per worktree action (refresh/cleanup/reset/force-remove/batch-merge)

Replaces the shared IsBusy/IsMerging flags in WorktreesOverviewModalViewModel and the
reset flow in WorktreesSettingsTabViewModel with dedicated OperationStatus instances
shown via OperationIndicator, so a running Refresh no longer blocks the Cleanup
indicator. ForceRemove gains a CanExecute guard against re-entrancy while it's running,
and the reconcile tick's busy guard now checks all four action statuses instead of the
old IsBusy||IsMerging pair.

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

@@ -98,7 +98,7 @@ public class WorktreesOverviewBatchMergeTests
         Assert.Equal(BatchMergeOutcome.Blocked, a.MergeOutcome);
         Assert.Equal(BatchMergeOutcome.Failed, b.MergeOutcome);
         Assert.Empty(vm.ConflictRows);
-        Assert.False(vm.IsMerging);
+        Assert.False(vm.BatchMergeStatus.IsRunning);
     }
 
     [Fact]
@@ -164,7 +164,40 @@ public class WorktreesOverviewBatchMergeTests
         Assert.False(vm.MergeAllCommand.CanExecute(null));
         vm.SelectedTarget = "main";
         Assert.True(vm.MergeAllCommand.CanExecute(null));
-        vm.IsMerging = true;
-        Assert.False(vm.MergeAllCommand.CanExecute(null));
+        using (vm.BatchMergeStatus.Begin("merging"))
+        {
+            Assert.False(vm.MergeAllCommand.CanExecute(null));
+        }
+        Assert.True(vm.MergeAllCommand.CanExecute(null));
+    }
+
+    [Fact]
+    public void MergeAll_CanExecuteChanged_fires_when_batch_status_changes()
+    {
+        var vm = NewVm();
+        var a = ActiveRow("a"); a.IsChecked = true;
+        vm.AddRowForTest(a);
+        vm.SelectedTarget = "main";
+
+        var raised = 0;
+        vm.MergeAllCommand.CanExecuteChanged += (_, _) => raised++;
+
+        using (vm.BatchMergeStatus.Begin("merging")) { }
+
+        Assert.Equal(2, raised);
+    }
+
+    [Fact]
+    public void ForceRemove_canExecute_is_false_while_a_removal_is_in_flight()
+    {
+        var vm = NewVm();
+        var row = ActiveRow("a");
+
+        Assert.True(vm.ForceRemoveCommand.CanExecute(row));
+        using (vm.ForceRemoveStatus.Begin("removing"))
+        {
+            Assert.False(vm.ForceRemoveCommand.CanExecute(row));
+        }
+        Assert.True(vm.ForceRemoveCommand.CanExecute(row));
     }
 }