Carry one persisted region record through an ordered chain of steps.
Each step sees only a frozen copy of the record — never the store, never a
caller's options — and its output is checked before the next step runs, so a
migration that rewrites an identity fails the record instead of quietly
repartitioning it. Exported so a host can rehearse a ladder against a record
without an IndexedDB transaction.
Carry one persisted region record through an ordered chain of steps.
Each step sees only a frozen copy of the record — never the store, never a caller's options — and its output is checked before the next step runs, so a migration that rewrites an identity fails the record instead of quietly repartitioning it. Exported so a host can rehearse a ladder against a record without an IndexedDB transaction.