Provide ability to render video to a file

E.g. by rendering the `VideoView` node hierarchy frame-by-frame to an image buffer ([see here](https://stackoverflow.com/questions/20625378/how-to-render-a-sknode-to-uiimage)) and then into a video encoder.

Start by tracing the VideoView node hierarchy mentioned in the issue and review how frames are currently represented. Determine the project’s existing video output or encoding entry points, then verify that rendering the hierarchy frame by frame produces a playable file. No specific files or tests are named in the issue.

Written by the indexing model from the issue text.