feat: the invoice PDF, with stamps and each payment (P4b S3)

ledger-import invoice_pdf (templates/invoice.typ): seller, bill-to,
number, dates, terms, lines, total, each settled line and the balance
due; money formatted in Rust (the template does no arithmetic), text as
data, deterministic bytes. Stamps as a rubber stamp would mark it, in
red: PAID (with the day it was paid in full: the invoice is then the
customer's receipt), PARTIALLY PAID, PAST DUE, VOID; DRAFT in gray for
S4's preview. ledger-package invoice_document builds it from the books
as of a day: the derived figures (B-38), each payment that stands on its
own line with its date, payment method and reference; re-created copies
say so (the issued copy is kept from S4 on and never changes).
books.document pdf hands it over as a download; the viewer's invoice
page saves or opens it. The owner asked for the paid stamp with the
payment's date and details (2026-10-24).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

plan/STATUS.md

@@ -235,7 +235,15 @@ tie-out in `books.verify` and `control_problems` in `books.digest`; the
 over-the-wire test `documents_void_and_tie_out_over_the_wire`. Still for
 later slices: the processor fee on a payment (S6, with multi-document
 payments and discounts), Needs attention in the viewer for the control
-check, and S2 to S7.
+check, and S2 to S7. S2 (2026-10-24): `books.documents`,
+`books.document`, and the viewer's Invoices & Bills (Money in, Money out,
+a document's page, overview tiles). S3 (2026-10-24): the invoice PDF
+(`ledger-import` `invoice_pdf`, `templates/invoice.typ`; `ledger-package`
+`invoice_document`): re-created from the books, each payment on its own
+line with its date, method and reference, stamped PAID with the day,
+PARTIALLY PAID, PAST DUE or VOID (DRAFT, gray, for S4's preview); by
+download from `books.document pdf`, and Save invoice PDF in the viewer.
+The copy issued is kept from S4 on and never changes.
 **Still open after P3 (each for the phase named, or the lead):**
 - Invoices and bills take a project now (above), behind the new journal
   feature `document_line_projects`: the first company's books declared