invoicing.first_number's refusal (LedgerError::FirstNumberLocked) lands
as the contract the store's check raises once invoices carry numbers
(S4.3): a series that has begun is never renumbered (B-40, A-2).
Also: the settings invariants name the number prefix's bound, update_party's
doc says which facts wait for documents_v2, and the email check no longer
reads as a single-arm match. Terms is S4.1's as it landed; this slice no
longer carries a copy.
swaits
962b52c991