Upscale a previously generated video to twice its resolution (2x). Pass the video `url` you received from `createVideo`, `createVideoFromReferences`, or `editVideo` — it must be a video you generated within the last 7 days; arbitrary external videos are not accepted. Only videos below 960x960 pixels can be upscaled (larger sources are rejected). Synchronous: the call blocks until upscaling finishes and returns the new video URL and its duration in seconds. Billed per second of video, independent of model, charged only on success. Pass an optional `request_id` to tag the result so you can locate it later via `getVideoResults`. Related tools: `createVideo` for image-to-video, `editVideo` to modify a generated video. Requires an API key (user scope).