Petri's retention decides whether a released workspace is kept or removed.
Fabro's lifecycle settings decide whether a sandbox keeps running after
the run and whether a delete may remove it; none asks for removal at the
run's end, and the sandbox tab, `fabro cp`, the run's delete and the
sandbox scenarios read the container after the run. So the mapping is
`Retention::Always` for every setting, named once as `engine::RETENTION`
with the reasoning, instead of a per-setting function that released a
finished sandbox.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>