Remix a Sora video with a new prompt.

Request Fields:

• video_id: The ID of the previous video to remix (required)
• prompt: New prompt describing the remix changes (required)
• domain_id: Optional domain ID for organizing the asset

Example:

{
  "video_id": "video_abc123...",
  "prompt": "Shift the color palette to teal, sand, and rust, with a warm backlight.",
  "domain_id": "optional-domain-id"
}

Returns a task_id and async_task_id. The video will be processed in the background:

1. Polls for video completion
2. Downloads and uploads to S3
3. Saves to Assets table with type=video, sub_type=sora_video

Use the async_task_id to check status via AsyncTask endpoint.