Why: U3 seeds a directory revision in every new target database, which made an empty PostgreSQL target look occupied to the migration guard.
Evidence: Isolated PostgreSQL cmd/storage-migrate integration tests passed after the previously failing cases reproduced the error.
Impact: A fresh target remains eligible for migration; existing business rows and foreign migration identities still block it.
Refs: IAM U3 Stage 7; docs/proposals/2026-10-14-iam-u3-account-contract-and-plan.md §10