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.
implementer
f6d407394d