[Model] Add Cache-DiT and CPU offload support for SANA-Video 2B (#5882)

Signed-off-by: cr-gao <gaochenrui@sjtu.edu.cn>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>
Co-authored-by: Alicia <115451386+congw729@users.noreply.github.com>

vllm_omni/diffusion/worker/diffusion_model_runner.py

@@ -631,6 +631,12 @@ class DiffusionModelRunner(OmniConnectorModelRunnerMixin):
         # RequestBatchSamplingParamsKey, so the first request's num_inference_steps applies
         # to the whole runner batch.
         num_inference_steps = first_req.sampling_params.num_inference_steps
+        if num_inference_steps is None and first_req.sampling_params.timesteps is not None:
+            num_inference_steps = len(first_req.sampling_params.timesteps)
+        if num_inference_steps is None and first_req.sampling_params.sigmas is not None:
+            num_inference_steps = len(first_req.sampling_params.sigmas)
+        if num_inference_steps is None:
+            num_inference_steps = getattr(self.pipeline, "default_num_inference_steps", None)
         if num_inference_steps is None and od_config.cache_backend in (
             "tea_cache",
             "step_cache",