Possibility to export with transparent background

If Animation Maker could work and export with a transparent background it would be perfect to use as a complement in a video editor.

The issue requests transparent-background export for use in a video editor, but names no files, export format, entry point, or acceptance criteria. Start by tracing the existing export path and identifying which supported output formats can preserve transparency. Done means an exported animation retains a transparent background in a supported video-editor workflow.

Written by the indexing model from the issue text.