[Core] Add realtime AR-Diffusion tick sessions for LingBot World 2.0 (#5491)

Signed-off-by: zhangbin.327 <zhangbin.327@bytedance.com>
Signed-off-by: Jack47 <scsvip@gmail.com>
Co-authored-by: zhangbin.327 <zhangbin.327@bytedance.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>

tests/entrypoints/test_utils.py

@@ -417,8 +417,9 @@ class TestTryResolveOmniModelType:
 
 class TestLoadAndResolveStageConfigs:
     def test_load_and_resolve_with_kwargs(self, mocker: MockerFixture):
-        """Ensure that dtype survives default stage creation."""
-        kwargs = {"dtype": torch.float32}
+        """Ensure that kwargs survive default stage creation."""
+        engine_backend = "vllm_omni.experimental.ar_diffusion.engine.ARDiffusionEngine"
+        kwargs = {"dtype": torch.float32, "engine_backend": engine_backend}
         mocker.patch("vllm_omni.entrypoints.utils.resolve_model_config_path", return_value=None)
         mocker.patch("vllm_omni.entrypoints.utils.load_stage_configs_from_model", return_value=([], None))
 
@@ -431,6 +432,7 @@ class TestLoadAndResolveStageConfigs:
         assert config_path is None
         assert len(stage_configs) == 1
         assert "dtype" in stage_configs[0]["engine_args"]
+        assert stage_configs[0]["engine_args"]["engine_backend"] == engine_backend
 
     def test_deploy_config_preserves_cli_overrides_and_replicas(self, tmp_path, mocker: MockerFixture):
         deploy_path = tmp_path / "qwen3_multi.yaml"