[Refactor] Remove dead legacy pipeline.yaml loader and duplicate diff… (#4023)

Signed-off-by: dph97 <nenbaying@163.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: zhuhonghan <z00806815@china.huawei.com>

tests/entrypoints/test_omni_sleep_mode.py

@@ -532,7 +532,10 @@ async def test_pure_diffusion_scenario(tp_size: int):
     try:
         await engine.sleep(level=1)
         await engine.wake_up()
-        async for _ in engine.generate("test", sampling_params=SamplingParams()):
+        async for _ in engine.generate(
+            "test",
+            sampling_params=OmniDiffusionSamplingParams(num_inference_steps=2, height=256, width=256),
+        ):
             pass
         logger.info("Pure diffusion OK (TP=%s)", tp_size)
     finally: