The implementer caught that claims.id is a single-column PK, which
prevents the same CLM01 from existing in multiple batches. That
makes the spec's pre-flight 409 workflow unreachable and resubmits
impossible. Migration 0014 relaxes the PKs to composite (batch_id,
id) on both claims and remittances, and updates all FKs that
referenced the old single-column PK. Task 1.3 in the plan is now
the migration; the previous Task 1.3 (helper tightening) is
renumbered to Task 1.4 and will run after 0014 lands.
Tyler