Describe and demonstrate the bug

the transcript tests don't fully get initialized if the ucm binary hasn't changed. (this is intentional, because they are slow and we don't need to rerun them if the binary hasn't changed.)

part of that initialization is making the unison binary available.

the unison binary is required for the ddl-ffi-* smoke tests.

that said, the smoke tests also don't need to run in the case that the ucm binary hasn't changed either, so they should be behind the same condition as the rest of the transcript tests.

https://github.com/unisonweb/unison/actions/runs/19771013851/job/56829585948?pr=6022

cc @dolio

Additional context
Add any other context about the problem here.