[Bagel]: Support think mode in single stage deployment of Bagel

[princepride]

PLEASE FILL IN THE PR DESCRIPTION HERE ENSURING ALL CHECKLIST ITEMS (AT THE BOTTOM) HAVE BEEN CONSIDERED.

Purpose

Support think mode in single stage deployment of Bagel.

Test Plan

python3 examples/offline_inference/bagel/end2end.py --model ByteDance-Seed/BAGEL-7B-MoT   --stage-configs-path vllm_omni/model_executor/stage_configs/bagel_single_stage.yaml   --think --modality text2img

python3 examples/offline_inference/bagel/end2end.py --model ByteDance-Seed/BAGEL-7B-MoT   --stage-configs-path vllm_omni/model_executor/stage_configs/bagel_single_stage.yaml   --think --modality img2img --image-path women.jpg   --prompts "Let the woman wear a blue dress"

Test Result

<think>
The model should generate an image of a small, fluffy cat with soft fur and a friendly expression.
Here’s the expanded prompt: A small, fluffy cat with soft, dense fur in warm tones like cream or light brown, featuring a gentle and friendly facial expression with large, expressive eyes and a slightly open mouth showing a hint of a smile. The setting is minimalistic and softly lit to emphasize the cat's delicate features, with a neutral background that enhances its charm without distraction. Ultra-realistic rendering with fine details capturing the texture of the fur and subtle shadows for depth.
</think>

<think>
The user wants the woman's dress color changed to blue while keeping the rest of the image unchanged. The structure, layout, and background should remain the same, ensuring only the dress color is altered to blue.
</think>

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[princepride]

@natureofnature PTAL

[princepride]

I compared single stage deployment and multi stage deployment result. I found their totally different! Including think mode or non think mode, img2img or text2img.