fix(diffusion): address Wan auto decode review feedback

Signed-off-by: Hongsheng Liu <liuhongsheng4@huawei.com>

tests/diffusion/test_diffusion_model_runner.py

@@ -732,19 +732,6 @@ def test_execute_model_runs_forward_after_kv_receive(monkeypatch):
 @pytest.mark.core_model
 @pytest.mark.cpu
 def test_load_model_clears_cache_backend_for_unsupported_pipeline(monkeypatch):
-    memory_pool_active = False
-    preparation_pool_states = []
-
-    @contextmanager
-    def _memory_pool_context(tag):
-        nonlocal memory_pool_active
-        assert tag == "weights"
-        memory_pool_active = True
-        try:
-            yield
-        finally:
-            memory_pool_active = False
-
     class _DummyLoader:
         def __init__(self, load_config, od_config=None):
             del load_config, od_config
@@ -792,22 +779,16 @@ def test_load_model_clears_cache_backend_for_unsupported_pipeline(monkeypatch):
     monkeypatch.setattr(model_runner_module, "LoadConfig", lambda: object())
     monkeypatch.setattr(model_runner_module, "DiffusersPipelineLoader", _DummyLoader)
     monkeypatch.setattr(model_runner_module, "DeviceMemoryProfiler", _DummyMemoryProfiler)
-    monkeypatch.setattr(
-        model_runner_module,
-        "prepare_pipeline_wan_spatial_shard_decode",
-        lambda pipeline: preparation_pool_states.append(memory_pool_active),
-    )
     monkeypatch.setattr(model_runner_module, "get_offload_backend", lambda od_config, device: None)
     monkeypatch.setattr(
         model_runner_module, "get_cache_backend", lambda cache_backend, cache_config: dummy_cache_backend
     )
 
-    DiffusionModelRunner.load_model(runner, memory_pool_context_fn=_memory_pool_context)
+    DiffusionModelRunner.load_model(runner)
 
     assert runner.cache_backend is None
     assert runner.od_config.cache_backend is None
     assert dummy_cache_backend.enabled is False
-    assert preparation_pool_states == [True]
 
 
 @pytest.mark.core_model