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-gui/src/pages/journal.rs

@@ -830,6 +830,14 @@ pub fn describe(b: &Books, line: &JournalLine) -> Option<Event> {
             format!("Bill paid, {}", amount(p)),
             entry_id.map(Route::Entry),
         ),
+        "invoice.written_off" => {
+            let invoice = p.get("invoice_id").and_then(|v| v.as_u64()).unwrap_or(id);
+            ev(
+                icon::HAND_COINS,
+                format!("Invoice {invoice} written off, {}", amount(p)),
+                entry_id.map(Route::Entry),
+            )
+        }
         "period.created" => ev(
             icon::CALENDAR_PLUS,
             format!("Period {} created", s(p, "name")),