test(#1749): 集成测试补变体0 clone mock（#1749 变体0 一律 clone_plan_for_variant）

tests/integration/test_generation_api.py

@@ -373,6 +373,8 @@ class TestCreateGenerationTask:
         mock_celery.send_task = MagicMock()
 
         with patch("app.services.edit_plan_service.EditPlanService") as MockPlanSvc:
+            # #1749：变体0 也 clone 源 plan（不污染源 plan），变体1/2 各自 reselect
+            MockPlanSvc.return_value.clone_plan_for_variant.return_value = MagicMock(id="variant-plan-0")
             MockPlanSvc.return_value.reselect_plan_for_variant.side_effect = [
                 MagicMock(id="variant-plan-1"),
                 MagicMock(id="variant-plan-2"),
@@ -398,8 +400,9 @@ class TestCreateGenerationTask:
         batch_ids = [t["batch_id"] for t in data["items"] if t["batch_id"]]
         assert len(batch_ids) == 3
         assert len(set(batch_ids)) == 1
-        # 变体 1/2 各自独立选片
+        # 变体 1/2 各自独立选片；变体 0 clone 源 plan（#1749）
         assert MockPlanSvc.return_value.reselect_plan_for_variant.call_count == 2
+        assert MockPlanSvc.return_value.clone_plan_for_variant.call_count == 1
 
     def test_create_task_project_not_found(self, client):
         """项目不存在返回 404。"""