[Feature]: Adds distilled LoRA support for diffusion models (#2783)

Signed-off-by: Songrui625 <songrui625@gmail.com>

tests/entrypoints/test_async_omni_diffusion_config.py

@@ -284,6 +284,37 @@ def test_serve_cli_accepts_diffusion_pipeline_profiler_flag():
     assert stage_cfg["engine_args"]["enable_diffusion_pipeline_profiler"] is True
 
 
+def test_serve_cli_forwards_distilled_lora_to_diffusion_stage():
+    """Ensure startup distilled LoRA options reach the online diffusion stage."""
+    parser = TrackingArgumentParser()
+    subparsers = parser.add_subparsers(dest="command")
+    OmniServeCommand().subparser_init(subparsers)
+
+    args = parser.parse_args(
+        [
+            "serve",
+            "Wan-AI/Wan2.2-T2V-A14B-Diffusers",
+            "--omni",
+            "--lora-backend",
+            "distill",
+            "--lora-path",
+            "/models/high.safetensors",
+            "/models/low.safetensors",
+        ]
+    )
+
+    explicit_kwargs = args.get_explicit_kwargs_dict()
+    stage_cfg = AsyncOmniEngine._create_default_diffusion_stage_cfg(explicit_kwargs)[0]
+    engine_args = stage_cfg["engine_args"]
+
+    assert explicit_kwargs["lora_backend"] == "distill"
+    assert engine_args["lora_backend"] == "distill"
+    assert engine_args["lora_path"] == [
+        "/models/high.safetensors",
+        "/models/low.safetensors",
+    ]
+
+
 def test_serve_cli_forwards_distributed_offload_residency():
     """Ensure the two-GPU DLO placement controls reach the diffusion stage."""
     parser = TrackingArgumentParser()