`/prone/latest` is not accessible

There is a [nice trick](https://github.com/magnars/prone#a-little-trick) in `prone` that makes the last error accessible via `prone/latest`.

However it doesn't seem to work with `catacumba-prone`.

Start by comparing the catacumba-prone integration with the linked prone “A Little Trick” documentation and trace how the latest error is exposed. Confirm the expected behavior by checking whether /prone/latest becomes accessible through catacumba-prone; the issue does not mention specific files or tests.

Written by the indexing model from the issue text.