[CI] Restructure vLLM-Omni Test Layout, Fixture Scope, and Support Modules (#2620)

Signed-off-by: wangyu <410167048@qq.com>

tests/e2e/offline_inference/test_sequence_parallel.py

@@ -20,8 +20,8 @@ import torch
 import torch.distributed as dist
 from PIL import Image
 
-from tests.conftest import OmniRunner
-from tests.utils import hardware_test
+from tests.helpers.mark import hardware_test
+from tests.helpers.runtime import OmniRunner
 from vllm_omni.diffusion.data import DiffusionParallelConfig
 from vllm_omni.inputs.data import OmniDiffusionSamplingParams
 from vllm_omni.platforms import current_omni_platform