创建视频续写任务

curl --location 'https://api.modellink.online/xai-video/v1/videos/extensions' \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--data '{
    "model": "grok-imagine-video",
    "prompt": "The camera slowly pulls back and reveals a lake in the distance",
    "duration": 5,
    "video": {
        "url": "https://cdn.example.com/source-video.mp4"
    }
}'