[Feature] Transfer AR-to-diffusion payloads over NIXL (#6264)

Signed-off-by: yuanwu <yuan.wu@intel.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>

tests/model_executor/models/test_minimax_h3_encoder_payload.py

@@ -91,8 +91,11 @@ def test_pipeline_owns_three_encoders_then_dit_and_decoders() -> None:
 
     encoder, diffusion = MINIMAX_H3_PIPELINE.stages
     assert encoder.model_arch == "MiniMaxH3Encoder"
-    assert encoder.custom_process_next_stage_input_func is None
+    assert encoder.custom_process_next_stage_input_func == (
+        "vllm_omni.model_executor.stage_input_processors.minimax_h3.encoder2diffusion_full_payload"
+    )
     assert diffusion.model_arch == "MiniMaxH3Pipeline"
+    assert diffusion.stage_input_payload_keys == ("encoder_output",)
     assert diffusion.requires_multimodal_data is False
     assert diffusion.requires_full_payload_input is False
 
@@ -441,7 +444,7 @@ def test_encode_media_keeps_audio_budgets_and_component_residency_separate(
     else:
         with pytest.raises(ValueError, match="at most 15 seconds"):
             encode_media(media, **kwargs)
-    assert scopes == [video_vae, audio_vae]
+    assert scopes == ([video_vae, audio_vae] if valid else [])
 
 
 def test_encoder_output_reuses_encoder_handoff_and_round_trips(monkeypatch) -> None: