DoubaoStreamPartialSucceeded(图片生成成功事件)

{
    "type": "image_generation.partial_succeeded",
    "model": "doubao-seedream-4-0-250828",
    "created": 1589478378,
    "image_index": 0,
    "url": "https://example.com/generated-image.jpg",
    "size": "2048×2048"
}