Node's type stripping does not rewrite './ledger.js' to './ledger.ts', so the
runner's runtime import of the ledger could not resolve when the behavioral
probes execute the committed runner.ts directly (CI failure on Node 24).
The ledger is now imported type-only and the caller passes the instance
(new MigrationLedger(pool)) — the probes already do. runner.ts has no
runtime imports left, so type stripping erases them and the committed
module loads as-is.
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