The first PA.f37 freeze test only retires the farmer, who holds a routine and
an obligation but no dependency, so it never exercised `derive_motion`'s
dependency-loop retired check. Mutation testing against commit bc1852d
confirmed the gap: disabling that loop's `is_retired` skip passed the full
suite. This adds the other half — retiring the reeve, who holds the goal and
the Bind dependency, while the farmer stays live — which kills that mutation.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
33fc9c671d