feat(ui): attach MergeModal to DetailsIsland

src/ClaudeDo.Ui/Views/Islands/DetailsIslandView.axaml.cs

@@ -36,6 +36,14 @@ public partial class DetailsIslandView : UserControl
                 await modal.ShowDialog(owner);
             };
 
+            vm.ShowMergeModal = async (mergeVm) =>
+            {
+                var owner = TopLevel.GetTopLevel(this) as Window;
+                if (owner == null) return;
+                var modal = new MergeModalView { DataContext = mergeVm };
+                await modal.ShowDialog(owner);
+            };
+
             vm.ConfirmAsync = ShowConfirmAsync;
         }
     }