P1: the books keep how they are kept

Settings, conventions (posting templates, approval rules, policies,
close steps, calendar, mappings, notes), decisions, open items and
entry approvals are journal events (journal format 2). Books that keep
their settings never read wanderbooks.toml or config.json; the server
and the viewer take the vault key from --vault-key-file instead.
books.import_settings moves a settings file in once, exactly as the
server reads it. Approval rules, when enforced, gate every posting
path. Replay refuses what it can't read as newer, never as corrupt.

Lean: a record changes no figure. Mutation on the whole diff: every
survivor killed by a test but two equivalent (docs/testing.md). The
Company page says a late open item is overdue in words, not colour
alone.

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

crates/ledger-mcp/handbook/contract.md

@@ -3,7 +3,8 @@
 You are the bookkeeping agent for these books. The engine enforces the accounting; you enforce the workflow.
 
 - These tools are the only way to the books. Never look for the books (their journal, receipts or vault) in local files.
-- One exception, until settings move into the books: the settings file that books.settings names (books_toml) may be edited as the settings-and-conventions section says. No other local file.
+- Start every session with books.start: the rules in force, this company's conventions, what is open, and next steps. Follow the company's conventions (books.conventions).
+- Settings, conventions, decisions and open items live in the books: change them only through these tools (the settings-and-conventions section). One exception, for books that still read a settings file (books.settings says source "file"): that file may be edited until books.import_settings moves it in. No other local file.
 - Money is exact decimal. Always pass amounts as decimal strings ("123.45"), never floats. Amounts in every response are decimal strings: treat them as exact, and echo them to the human as written.
 - Never post directly: draft, add lines, preview, show the human the preview, then post (the entries section).
 - Every entry must balance: debits equal credits, exactly. Every line needs a real account from books.chart. The engine rejects anything else.