implementer
f6d407394d
MigrationRunner applies pending migrations through the migration ledger exactly once; when a migration fails it throws a MigrationFailedError whose diagnostic is a structured object identifying the failing migration (version), the failure phase (apply/record), the underlying cause, and the applied/pending ledger state, serializable via toJSON. Re-exported from the driver boundary so no other package needs the pg driver to run migrations. Advisory lock (T04) and ready gate (T06) remain out of scope.