Why I Made the Ledger Refuse Single Rows

The bug I kept designing around was not "wrong penalty amount." Wrong amounts are visible. A supplier sees a credit note for EUR 8400, checks the contract, and pushes back. The operator can investigate. The trail exists. The quieter failure is a penalty row with no mirror. One side of the system says the buyer is owed money. The other side never records the supplier-facing debit. The total looks correct in the dashboard because the credit row exists. The settlement builder can even pick it up. B