[Refactor 1/N] Centralize Omni config resolution (#5140)

Signed-off-by: Chenguang ZHENG <645327136@qq.com>

tests/diffusion/models/minimax_h3/test_minimax_h3_contract.py

@@ -177,9 +177,9 @@ def _write_partition_index(path, *, partition, tasks):
 
 
 def test_modular_diffusers_index_is_resolved_generically(tmp_path):
+    from vllm_omni.config.resolver import resolve_omni_config
     from vllm_omni.diffusion.data import OmniDiffusionConfig, resolve_model_class_name
     from vllm_omni.diffusion.utils.hf_utils import is_diffusion_model
-    from vllm_omni.entrypoints.utils import resolve_model_config_path
 
     (tmp_path / "modular_model_index.json").write_text(
         json.dumps(
@@ -193,7 +193,16 @@ def test_modular_diffusers_index_is_resolved_generically(tmp_path):
 
     assert is_diffusion_model(str(tmp_path))
     assert resolve_model_class_name(str(tmp_path)) == "MiniMaxH3ModularPipeline"
-    assert resolve_model_config_path(str(tmp_path)) is None
+    resolved = resolve_omni_config(
+        str(tmp_path),
+        trust_remote_code=False,
+        deploy_config_path=None,
+        cli_overrides=None,
+        stage_overrides=None,
+        strategy_config_path=None,
+    )
+    assert resolved.config_path is None
+    assert resolved.stage_by_id(0).engine_args.model_class_name == "MiniMaxH3ModularPipeline"
 
     config = OmniDiffusionConfig(model=str(tmp_path))
     config.enrich_config()