Why: SQLite coverage cannot prove PostgreSQL CAS and multi-row migration rollback.
Evidence: SELF /tmp/project-settings-postgres-business-20261014-973d52c1.json ran two real PostgreSQL business tests in a fresh local cluster and stopped that cluster afterward.
Impact: Add opt-in isolated database checks for two-connection CAS, private settings boundaries, default restoration, injected migration rollback and idempotent replay. These tests do not select deployment credentials.
Refs: P8, docs/records/2026-10-14-rdm-settings-completion-contract.md