feat(ui): dirty Ziel-Verzeichnis beim Oeffnen des Merge-Dialogs melden statt nach dem Fehlschlag

MergeTargetsDto/MergeTargets bekommen TargetDirty (via HasChangesAsync,
includeUntracked: false). Das Merge-Modal zeigt Warnung + Stash-Retry
sofort in InitializeAsync statt erst nach dem dirty_target-Fehlschlag;
der REVIEW-Block in der Detail-Pane zeigt denselben Hinweis neben
Approve. Der dirty_target-Rueckgabepfad bleibt als Absicherung bestehen.

Behebt Befund F6 aus docs/test-session-2026-09-16.md.

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

@@ -726,6 +726,7 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase, IDisposable
                     Merge.MergeTargetBranches.Clear();
                     foreach (var b in targets.LocalBranches) Merge.MergeTargetBranches.Add(b);
                     Merge.SelectedMergeTarget = targets.DefaultBranch;
+                    Merge.TargetDirty = targets.TargetDirty;
                 }
             }
             await Merge.RefreshMergePreviewAsync();
@@ -776,6 +777,7 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase, IDisposable
                         foreach (var b in targets.LocalBranches)
                             Merge.MergeTargetBranches.Add(b);
                         Merge.SelectedMergeTarget = targets.DefaultBranch;
+                        Merge.TargetDirty = targets.TargetDirty;
                     }
                 }
             }
@@ -822,6 +824,7 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase, IDisposable
                         foreach (var b in targets.LocalBranches)
                             Merge.MergeTargetBranches.Add(b);
                         Merge.SelectedMergeTarget = targets.DefaultBranch;
+                        Merge.TargetDirty = targets.TargetDirty;
                     }
                 }
             }

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

@@ -28,6 +28,10 @@ public sealed partial class MergeSectionViewModel : ViewModelBase
     [ObservableProperty] private ObservableCollection<string> _mergeTargetBranches = new();
     [ObservableProperty] private string? _selectedMergeTarget;
 
+    // Mirrors MergeTargetsDto.TargetDirty — surfaced next to Approve so a dirty target working
+    // dir is visible before anyone clicks, not just after the merge modal refuses it.
+    [ObservableProperty] private bool _targetDirty;
+
     // No CanExecute to gate here — RefreshMergePreviewAsync is triggered from the Bind path,
     // not a [RelayCommand], so PreviewOp only drives the indicator, never locks a button.
     public OperationStatus PreviewOp { get; } = new();
@@ -141,6 +145,7 @@ public sealed partial class MergeSectionViewModel : ViewModelBase
         MergePreviewText = "";
         MergeIsClean = false;
         MergeIsConflict = false;
+        TargetDirty = false;
         SyncWorktree(null, null, null, null, null);
         SyncTaskContext(null, null, false);
         SyncChildOutcomes(false, 0);

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

@@ -76,6 +76,14 @@ public sealed partial class MergeModalViewModel : ViewModelBase
             SelectedBranch = Branches.Contains(targets.DefaultBranch)
                 ? targets.DefaultBranch
                 : Branches.FirstOrDefault();
+
+            // Known dirty before anyone clicks Merge — offer the stash retry right away instead
+            // of making the user hit the "dirty_target" refusal first.
+            if (targets.TargetDirty)
+            {
+                WarningMessage = Loc.T("vm.merge.targetDirty");
+                ShowStashRetry = true;
+            }
         }
         catch (Exception ex)
         {

src/ClaudeDo.Ui/Views/Islands/Detail/WorkConsole.axaml

@@ -327,6 +327,10 @@
                 <ComboBox ItemsSource="{Binding Merge.MergeTargetBranches}"
                           SelectedItem="{Binding Merge.SelectedMergeTarget, Mode=TwoWay}"
                           HorizontalAlignment="Stretch" />
+                <TextBlock Classes="meta" Text="{loc:Tr details.workConsole.targetDirty}"
+                           TextWrapping="Wrap"
+                           Foreground="{DynamicResource AmberBrush}"
+                           IsVisible="{Binding Merge.TargetDirty}" />
               </StackPanel>
 
               <StackPanel Spacing="0">

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

@@ -70,6 +70,11 @@
                    TextWrapping="Wrap"
                    IsVisible="{Binding ErrorMessage, Converter={x:Static ObjectConverters.IsNotNull}}" />
 
+        <TextBlock Text="{Binding WarningMessage}"
+                   Foreground="{DynamicResource AmberBrush}"
+                   TextWrapping="Wrap"
+                   IsVisible="{Binding WarningMessage, Converter={x:Static ObjectConverters.IsNotNull}}" />
+
         <Button Classes="btn" HorizontalAlignment="Left"
                 Content="{loc:Tr modals.merge.stashAndMerge}"
                 Command="{Binding StashAndMergeCommand}"