[Feature][Bagel] Add CFG parallel mode (#1578)

Signed-off-by: Ding Zuhao <e1583181@u.nus.edu>
Signed-off-by: 汪志鹏 <wangzhipeng628@gmail.com>
Co-authored-by: 汪志鹏 <wangzhipeng628@gmail.com>

vllm_omni/diffusion/diffusion_engine.py

@@ -360,6 +360,9 @@ class DiffusionEngine:
                 # classifier-free guidance with an empty negative prompt.
                 guidance_scale=0.0,
                 num_outputs_per_prompt=1,
+                # Disable CFG for warmup to avoid triggering CFG parallel
+                # validation when cfg_parallel_size > 1.
+                extra_args={"cfg_text_scale": 1.0, "cfg_img_scale": 1.0},
             ),
         )
         logger.info("dummy run to warm up the model")