feat(audit): books.audit, the attestation tools and the CPA gate (P8)

The whole re-audit through the tools: books.audit previews its checks, then
with the preview's digest runs them, files the workpaper and journals the
run; the same books, day and scope return the run that exists.
books.attest_receipt, books.review_entry and books.attest_period record a
named client's claim with its self-reported method; books.attestations
weighs each against policy.attestation_bar as it stands. Under
policy.cpa_package_requires_audit = refuse, books that declared audits
cannot export the CPA package without a counted audit for the handoff at the
current head unless a reason is given, which is journaled as a decision
(D-9). Needs attention asks for the month-end attestation, the annual audit
and the audit before the handoff. Rules B-45, the handbook section, the
interface, parity, receipt-store and testing records, and the As-built
block. Merge needs no go-ahead: the live books refuse the new writes until
the owner gives it.

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

crates/ledger-cli/tests/spec_mcp.rs

@@ -1146,6 +1146,28 @@ fn happy_path(name: &str) -> Mcp {
         json!({"period_id": p, "confirmed": true}),
     );
 
+    // P8: an audit of the month, its workpaper, and the claims that stand
+    // behind it.
+    let audit_run = m.ok(
+        "books.audit",
+        json!({"scope": "month", "through": "2026-01-31", "confirmed": true}),
+    )["run"]["id"]
+        .as_u64()
+        .unwrap();
+    m.ok("books.workpaper", json!({"id": audit_run}));
+    let audited = m.attach(Some(e1), b"audit receipt");
+    m.ok(
+        "books.attest_receipt",
+        json!({"attachment_id": audited, "entry_id": e1, "amount": "10000.00",
+               "date": "2026-01-02", "method": {"reasoning_effort": "high"}}),
+    );
+    m.ok(
+        "books.review_entry",
+        json!({"entry_id": e1, "method": {"reasoning_effort": "high"}}),
+    );
+    m.ok("books.attestations", json!({}));
+    m.ok("books.attest_period", json!({"period": "2026-01"}));
+
     // How the books are kept: start, conventions, decisions, open items,
     // a template and an approval, and the settings file moving in.
     m.ok("books.start", json!({}));