feat(audit): audit runs and attestations are journaled (P8)

A claim that someone checked the books is evidence the CPA handoff rests on,
so it is a journal fact and replays: audit.run (a programme run through a
day at the books' figure head, with the hashes that make it reproducible and
the two filed workpapers), receipt.attested, entry.reviewed and
period.attested. Behind the journal feature audits, schema 20; no figure
moves. The figure head is the last line that bears on a figure: filing a
workpaper, a run or an attestation never makes an audit stale, an entry,
document, close, settings or role change does, so a period is attested only
on an audit that still describes the books. A receipt reading that differs
from the entry is recorded as disagreeing and never counts; whether a claim
counts is derived against the bar when asked, never stored.

The store also reads what a ledger cannot: the chain, the database against
a replay, stored and extracted files, the access log, duplicate files, and
the backups' standing handed in by the server. Fixture old-books/p8_before
was written by the version before this one and opens to its figures.
period.attested was the tests' placeholder for an unknown event type; they
use ledger.not_yet_written now.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HS8WZziDnyxunC23MUxrLp

crates/ledger-store/tests/fixtures/old-books-writer/src/bin/p8_before.rs

@@ -0,0 +1,85 @@
+//! Writes `p8_before`: books the version before P8 (main b97234ac) wrote
+//! through its Store API: a receipted opening and purchase, a 40.00
+//! purchase with no receipt, a small one under the threshold, a reversal,
+//! an invoice with a part payment, an open draft, and a closed January.
+//! No audit run, attestation or attestation setting exists in that
+//! version; this version opens the same journal and must report the same
+//! figures, and an audit of it finds exactly the missing receipt and the
+//! open draft.
+use chrono::NaiveDate;
+use ledger_core::{AccountType, Currency, DocumentLine, Money, Side};
+use ledger_store::Store;
+use rust_decimal::Decimal;
+use std::path::PathBuf;
+
+fn d(y: i32, m: u32, day: u32) -> NaiveDate {
+    NaiveDate::from_ymd_opt(y, m, day).unwrap()
+}
+fn cents(c: i64) -> Decimal {
+    Decimal::new(c, 2)
+}
+fn usd(c: i64) -> Money {
+    Money::new(cents(c), Currency::USD)
+}
+
+fn main() {
+    let root = PathBuf::from(std::env::args().nth(1).unwrap());
+    let dir = root.join("p8_before");
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let mut s = Store::create(&dir, Currency::USD).unwrap();
+    let bank = s.add_account("1000", "Bank", AccountType::Asset, None, false).unwrap();
+    let capital = s.add_account("3000", "Capital", AccountType::Equity, None, false).unwrap();
+    let sales = s.add_account("4000", "Sales", AccountType::Revenue, None, false).unwrap();
+    let rent = s.add_account("6000", "Rent", AccountType::Expense, None, false).unwrap();
+    let software = s.add_account("6100", "Software", AccountType::Expense, None, false).unwrap();
+    let post = |s: &mut Store, date: NaiveDate, what: &str, dr: u64, cr: u64, c: i64| {
+        let e = s.create_entry(date, what).unwrap();
+        s.add_line(e, dr, Side::Debit, usd(c)).unwrap();
+        s.add_line(e, cr, Side::Credit, usd(c)).unwrap();
+        e
+    };
+    let seed = post(&mut s, d(2026, 1, 1), "Opening capital", bank, capital, 100_000);
+    s.post_entry(seed).unwrap();
+    s.attach_receipt(Some(seed), "opening.txt", "text/plain", b"Opening deposit 1000.00 2026-01-01", None)
+        .unwrap();
+    let rent_jan = post(&mut s, d(2026, 1, 5), "January rent", rent, bank, 50_000);
+    s.post_entry(rent_jan).unwrap();
+    s.attach_receipt(Some(rent_jan), "rent.txt", "text/plain", b"Rent January 500.00 2026-01-05", None)
+        .unwrap();
+    // 40.00 is over the 25.00 threshold: no receipt, so an audit finds it.
+    let paper = post(&mut s, d(2026, 1, 7), "Printer paper", software, bank, 4_000);
+    s.post_entry(paper).unwrap();
+    // Under the threshold: needs none.
+    let stamps = post(&mut s, d(2026, 1, 8), "Stamps", software, bank, 1_200);
+    s.post_entry(stamps).unwrap();
+    let wrong = post(&mut s, d(2026, 1, 12), "Rent paid twice", rent, bank, 50_000);
+    s.post_entry(wrong).unwrap();
+    s.attach_receipt(Some(wrong), "rent2.txt", "text/plain", b"Rent again 500.00 2026-01-12", None)
+        .unwrap();
+    s.reverse_entry(wrong, d(2026, 1, 14), "Entered twice").unwrap();
+    let customer = s.add_customer("Fernhill Labs").unwrap();
+    let inv = s
+        .create_invoice(
+            customer,
+            d(2026, 1, 10),
+            d(2026, 2, 9),
+            vec![DocumentLine {
+                description: "Design".into(),
+                amount: cents(120_000),
+                class_id: None,
+                account: None,
+                quantity: None,
+                unit_price: None,
+            }],
+        )
+        .unwrap();
+    s.receive_payment(inv, d(2026, 1, 20), cents(40_000), bank).unwrap();
+    // An open draft in February; January closes around it.
+    let _open = post(&mut s, d(2026, 2, 12), "Coworking day pass", rent, bank, 3_500);
+    let jan = s.create_period("2026-01", d(2026, 1, 1), d(2026, 1, 31)).unwrap();
+    s.close_period(jan).unwrap();
+    let _ = sales;
+    s.verify().unwrap();
+    println!("WROTE {:?}", dir);
+}