docs(ui): clarify repo-import checkbox default intent

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

@@ -101,6 +101,7 @@ public sealed partial class RepoImportModalViewModel : ViewModelBase
                 Name = c.Name,
                 FullPath = c.FullPath,
                 AlreadyAdded = alreadyAdded,
+                // New repos start unchecked (no auto-select); already-added rows show ticked + disabled.
                 IsChecked = alreadyAdded,
             });
         }