chore(claude-do): Task-row visual fixes: chain step badge z-order + hide "#0"

From the 2026-08-11 unpushed-commit review (Low). Both in `src/ClaudeDo.Ui/Views/Islands/TaskRowView.axaml`. **Visual verification by the user is required — do not claim either is fixed without a screenshot; list both as open visual checks in the result.**

## A) Chain step badge is drawn under the task card

Commit `eb66ae7` moved `Border.chain-step-badge` from column 0 into column 1 with `Margin

ClaudeDo-Task: 9ec7d4ea-272b-4645-8da4-41ff3621f2f0

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

@@ -73,6 +73,10 @@ public sealed partial class TaskRowViewModel : ViewModelBase
     public int StepsCount { get; init; }
     public int StepsCompleted { get; init; }
 
+    // Number is 0 for rows created outside TaskNumberAllocator (test seeds, a future import
+    // path); a bare "#0" would be meaningless, so hide the badge entirely below 1.
+    public bool ShowNumberBadge   => Number > 0;
+
     public bool IsChild            => !string.IsNullOrEmpty(ParentTaskId);
     public bool IsAgentSuggested   => IsChild && !string.IsNullOrEmpty(CreatedBy) && CreatedBy == ParentTaskId;
     public bool IsPlanningParent => PlanningPhase != PlanningPhase.None
@@ -318,6 +322,7 @@ public sealed partial class TaskRowViewModel : ViewModelBase
         OnPropertyChanged(nameof(CanQueuePlan));
     }
 
+    partial void OnNumberChanged(int value)        => OnPropertyChanged(nameof(ShowNumberBadge));
     partial void OnBranchChanged(string? value)    => OnPropertyChanged(nameof(HasBranch));
     partial void OnWorktreeStateChanged(ClaudeDo.Data.Models.WorktreeState? value)
     {

src/ClaudeDo.Ui/Views/Islands/TaskRowView.axaml

@@ -34,15 +34,6 @@
                    HorizontalAlignment="Right" Margin="0,4"/>
       </Border>
 
-      <!-- Chain step badge: centered on the rail line, half laid over the card's left edge.
-           Lives in col 1 with a negative margin so it never widens the Auto indent column. -->
-      <Border Grid.Column="1" Classes="chain-step-badge"
-              IsVisible="{Binding ShowAsChainMember}"
-              HorizontalAlignment="Left" VerticalAlignment="Center"
-              Margin="-8,0,0,0">
-        <TextBlock Text="{Binding ChainStep}"/>
-      </Border>
-
       <!-- Main task card -->
       <Border Grid.Column="1" Classes="task-row"
               Margin="0,2"
@@ -84,6 +75,7 @@
           <Grid ColumnDefinitions="*,Auto" VerticalAlignment="Center">
             <Grid Grid.Column="0" ColumnDefinitions="Auto,*" VerticalAlignment="Center">
               <TextBlock Grid.Column="0" Classes="meta" Text="{Binding Number, StringFormat='#{0}'}"
+                         IsVisible="{Binding ShowNumberBadge}"
                          VerticalAlignment="Center" Margin="0,0,6,0"/>
               <TextBlock Grid.Column="1"
                          Classes="task-title"
@@ -232,6 +224,16 @@
         </Grid>
       </Border>
 
+      <!-- Chain step badge: centered on the rail line, half laid over the card's left edge.
+           Lives in col 1 with a negative margin so it never widens the Auto indent column.
+           Declared after the card so it paints on top instead of underneath it. -->
+      <Border Grid.Column="1" Classes="chain-step-badge"
+              IsVisible="{Binding ShowAsChainMember}"
+              HorizontalAlignment="Left" VerticalAlignment="Center"
+              Margin="-8,0,0,0">
+        <TextBlock Text="{Binding ChainStep}"/>
+      </Border>
+
     </Grid>
 
     <!-- Below-row indicator: only expands when visible (used for the last row of a section) -->

tests/ClaudeDo.Worker.Tests/UiVm/TaskRowViewModelTests.cs

@@ -40,6 +40,30 @@ public class TaskRowViewModelTests
         Assert.Equal(123, vm.Number);
     }
 
+    [Theory]
+    [InlineData(-1, false)]
+    [InlineData(0,  false)]
+    [InlineData(1,  true)]
+    [InlineData(42, true)]
+    public void ShowNumberBadge_Hides_For_Zero_And_Negative(int number, bool expected)
+    {
+        var vm = new TaskRowViewModel { Id = "t" };
+        vm.Number = number;
+        Assert.Equal(expected, vm.ShowNumberBadge);
+    }
+
+    [Fact]
+    public void ShowNumberBadge_Raises_PropertyChanged_On_Number_Change()
+    {
+        var vm = new TaskRowViewModel { Id = "t" };
+        var raised = new List<string?>();
+        vm.PropertyChanged += (_, e) => raised.Add(e.PropertyName);
+
+        vm.Number = 5;
+
+        Assert.Contains(nameof(TaskRowViewModel.ShowNumberBadge), raised);
+    }
+
     [Fact]
     public void IsDropTarget_Follows_Either_DropHint_And_Raises_PropertyChanged()
     {