fix: 修复统一渲染后遗留的测试引用

- test_1294_preview_voice_injection: 移除 _render_video() 调用中的 is_preview 参数
- test_generation_preview: 更新分辨率断言（预览不再设置自定义分辨率）

tests/unit/test_1294_preview_voice_injection.py

@@ -169,7 +169,6 @@ class TestRenderVideoVoiceInjection:
                 temp_path=Path("/tmp"),
                 output_name="test_output.mp4",
                 resolution="854x480",
-                is_preview=True,
                 voice_ids=["voice_abc"],
             )
 

tests/unit/test_generation_preview.py

@@ -1209,7 +1209,7 @@ class TestPreviewRouteAutoInfersVideoRatio:
     """验证预览路由在前端未传 video_ratio 时自动从模板推断。"""
 
     def test_auto_infer_pip_resolution(self):
-        """前端传 video_ratio=''，模板 mode=pip → resolution=480x854"""
+        """前端传 video_ratio=''，模板 mode=pip → resolution 为空（使用用户默认导出配置）"""
         from app.api.routes.generation_preview import create_preview_generation_task
         from app.schemas.generation_task import CreatePreviewGenerationTaskRequest
 
@@ -1254,7 +1254,7 @@ class TestPreviewRouteAutoInfersVideoRatio:
         # Verify the resolution passed to CreateGenerationTaskCommand
         call_args = MockUC.return_value.execute.call_args
         cmd = call_args[0][0]
-        assert cmd.resolution == "480x854", f"Expected 480x854, got {cmd.resolution}"
+        assert cmd.resolution == "", f"Expected empty resolution, got {cmd.resolution}"
 
 
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