feat(ui): Listen-Einstellungen — Checkbox fuer serialize_on_file_overlap

Das Flag war bisher nur ueber MCP set_list_config erreichbar. UpdateListConfigDto
fuehrt es tri-state (null = gespeicherten Wert behalten), damit nur das
Listen-Modal es setzen/loeschen kann und kein anderer Aufrufer es per Omission
verliert.

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

@@ -36,6 +36,9 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
     // Optional post-merge verification command (build/test), run in WorkingDir after a merge
     // lands; a non-zero exit keeps the task out of Done instead of silently reporting merged.
     [ObservableProperty] private string _verifyCommand = "";
+    // When on, the queue picker holds back a queued task whose declared scope globs overlap a
+    // running/awaiting-merge sibling in this list (ListConfigEntity.SerializeOnFileOverlap).
+    [ObservableProperty] private bool _serializeOnFileOverlap;
 
     public ObservableCollection<string> CommitTypeOptions { get; } = new(CommitTypeRegistry.Types);
 
@@ -71,6 +74,7 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
         await Agent.LoadForListAsync(listId, ct);
         var cfg = await _worker.GetListConfigAsync(listId);
         VerifyCommand = cfg?.VerifyCommand ?? "";
+        SerializeOnFileOverlap = cfg?.SerializeOnFileOverlap ?? false;
     }
 
     [RelayCommand]
@@ -84,7 +88,9 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
             IsManual,
             FindingsTracked));
 
-        await Agent.SaveAsync(string.IsNullOrWhiteSpace(VerifyCommand) ? null : VerifyCommand);
+        await Agent.SaveAsync(
+            string.IsNullOrWhiteSpace(VerifyCommand) ? null : VerifyCommand,
+            SerializeOnFileOverlap);
 
         CloseAction?.Invoke();
     }