[diffusion] feat: support default 4-step inference for Flux2-Klein distilled models (#17225)

Signed-off-by: Lancer <maruixiang6688@gmail.com>

python/sglang/multimodal_gen/test/server/testcase_configs.py

@@ -349,6 +349,14 @@ ONE_GPU_CASES_A: list[DiffusionTestCase] = [
         ),
         T2I_sampling_params,
     ),
+    DiffusionTestCase(
+        "flux_2_klein_image_t2i",
+        DiffusionServerArgs(
+            model_path="black-forest-labs/FLUX.2-klein-4B",
+            modality="image",
+        ),
+        T2I_sampling_params,
+    ),
     # TODO: replace with a faster model to test the --dit-layerwise-offload
     # TODO: currently, we don't support sending more than one request in test, and setting `num_outputs_per_prompt` to 2 doesn't guarantee the denoising be executed twice,
     # so we do one warmup and send one request instead