Rationale
The ledger, the handovers, the checkpoints and the session records stay under the caps the policy sets, so durable state does not grow without bound.
Required behaviour
The ledger, the handovers, the checkpoints and the session records stay under the caps the policy sets, and a cap is met by moving records aside, never by deleting one.
Failure behaviour
A violation is a FAIL finding under the category retention, and the command that found it exits 10. Under watch the same violation is reported as drift and the command exits 11.
Verification
mj_validate_retention decides it, dispatched from doctor, watch. The behavioural case test/cases/02_doctor_basic.sh proves it, and CI runs that case.