Determine which backend is currently used

Hey! Thanks for the great package.

Is there a way to figure out which backend is being used so I can generate different previews?

The issue names no files, tests, or entry points. Start by tracing how the package selects its backend and how consumers generate previews, then determine whether the active backend can be exposed. Done means there is a clear, usable way to identify the current backend, with behavior covered for the relevant selection paths.

Written by the indexing model from the issue text.