merge: P4b S7, bad debts (branch S7, 4b4fecb9)

The fourth of the paused branches: Ledger::write_off and the bad_debts
control role, invoice.written_off with its evidence filed in the same
store call, books.write_off_invoice, the write-off on the timeline and
in Needs attention, Lean writeOff_within_bounds, rules.md B-41 and the
bookspec examples. Twenty-eight files conflicted with the S4.4, S5 and
S6 merges; resolved as plan 8.0.2 says, keeping both sides' appends with
their seams restored, and: the scope table at 125; S7's law numbered 37;
B-41 placed before B-42; the handbook's step 4 and recovery procedures
folded into the one invoices-and-bills section; S7's wire tests in their
own module with the confirm S4.4's contract needs; S7's copy of the
payment steps dropped (S6 replaced them with Ledger::settle) and its
write-off journaled through S6's journal_auto_lines; in the old-books
fixture S7's hand-written write-off moved to a second invoice, since
S6's hand-written payment settles invoice 1 in full.

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

crates/ledger-core/src/lib.rs

@@ -77,8 +77,8 @@ pub use instruments::{Instrument, InstrumentId, InstrumentKind};
 pub use journal::{EntryId, EntryStatus, JournalEntry, JournalLine};
 pub use kernel::{EntryFlows, Flow};
 pub use ledger::{
-    ControlAccount, GENERAL_EXPENSES, Ledger, PAYABLES, PAYMENT_PROCESSING_FEES, PAYROLL,
-    PURCHASE_DISCOUNTS, RECEIVABLES, RETAINED_EARNINGS, REVENUE, ReconciliationReport,
+    BAD_DEBTS, ControlAccount, GENERAL_EXPENSES, Ledger, PAYABLES, PAYMENT_PROCESSING_FEES,
+    PAYROLL, PURCHASE_DISCOUNTS, RECEIVABLES, RETAINED_EARNINGS, REVENUE, ReconciliationReport,
     SALES_ALLOWANCES, UnclearedLine, control_account, control_accounts,
 };
 pub use money::{Currency, Money};