docs: sent tracking in the rules, parity and test records (P4b S5)

rules.md B-27 lists `documents_v2`, the one feature S4 to S7 share
(D-52), including `invoice.sent`; receipt-store.md lists the event;
parity.md gains the sent-tracking row (done: implemented, tested, and
golden-covered by the trial balance of the fixture book around a send);
testing.md records the tests and what P12 must mutate, and names the
two attention predicates as deferred with step 4 until U0b lands.

docs/parity.md

@@ -45,6 +45,7 @@ No other statuses.
 | 1099 vendor tracking + year-end worksheet | Vendors → Track payments for 1099; 1099 report | partial | hand-verified fixture (bill payments, card exclusion, reversal, year boundary); no golden file yet |
 | Prepaid expense + deferred revenue amortization | Amortization schedules (Xero/QBO add-ons) | partial | hand-verified fixture, to the cent; no golden file yet |
 | Automated cross-implementation diff harness (GnuCash first) | — (our `xtask oracle`) | todo | roadmap phase 3 |
+| Invoice sent tracking (who, how, to whom, when, original or reminder, the channel's reference) | Business → Invoices (Xero's "Sent"; QBO's email) | done | P4b S5; records, never sends (A-4); a send changes no figure; `invoice.sent` under `documents_v2` (D-52) |
 
 Workflow/UI parity (QuickBooks/Xero reference) gets its own catalog when the
 egui phase starts; semantics come first.
@@ -104,3 +105,14 @@ door on loopback for Caddy or a tunnel. `crates/ledger-cli/tests/two_user.rs`
 proves the account boundary and the move's head in CI
 (`.github/workflows/two-user.yml`); the recipe is `deploy/README.md`.
 The cutover rule in `docs/capability-parity.md` is unchanged.
+
+### P4b S5: sent tracking (2026-10-27)
+
+The catalog gains one row: an invoice's recorded sends. The books never
+send (A-4): `books.mark_sent` records who sent an invoice, how, to whom,
+when, whether it was the original or a reminder, and the channel's own
+reference, for an owner or a delegate such as an agent. The record is
+`invoice.sent`, under `documents_v2` (D-52), and it moves no figure, so
+the A/R and A/P rows' figures are unchanged. The floor never decreases:
+the row is `done`, tested by `sends_replay_and_project`,
+`a_send_changes_no_figure` and `mark_sent_records_who_and_how`.