feat(mcp): void, control check, payment method and reference (P4b S1, part B)

books.void_document voids an invoice or bill that should never have
existed by reversing its own entry with the reason (refused while a
payment stands on it, naming that payment). books.control_check ties
receivables and payables to their documents (B-23, B-38 INVARIANT 1):
balance, documents' total, lines that are no document's, the documents
needing attention; books.verify checks the identity and books.digest
lists its problems (control_problems). books.receive_payment and
books.pay_bill take instrument (tagged in the same call) and reference
(in the description), and answer the document's derived remaining and
status. The books record payments; they never collect or make them
(D-45). Docs, handbook and STATUS; the over-the-wire test
documents_void_and_tie_out_over_the_wire; the happy-path journey covers
both tools' output schemas. The processor fee waits for S6.

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

crates/ledger-cli/tests/mcp_journeys.rs

@@ -125,7 +125,7 @@ fn mcp_end_to_end() {
     // Tool listing: the narrow tools; chart is read-only.
     let list = mcp.request("tools/list", json!({}));
     let tools = list["result"]["tools"].as_array().unwrap();
-    assert_eq!(tools.len(), 118, "expected 118 tools, got {}", tools.len());
+    assert_eq!(tools.len(), 120, "expected 120 tools, got {}", tools.len());
     // Files come in as tool input: books.begin_upload, never a local path.
     assert!(tools.iter().any(|t| t["name"] == "books.begin_upload"));
     assert!(!tools.iter().any(|t| t["name"] == "books.import_local_file"));