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/tests/invoices.rs

@@ -336,3 +336,57 @@ fn an_overdue_invoice_with_an_old_send_is_asked_to_remind() {
     assert!(item.detail.contains("14 days overdue"), "{}", item.detail);
     assert!(item.prompt.contains("books.mark_sent"), "{}", item.prompt);
 }
+
+/// A written-off invoice (plan P4b S7): $500 issued, written off whole for
+/// a bad debt with its evidence, so it reads Written off owing nothing.
+fn write_off_books(dir: &TempDir) -> (u64, u64) {
+    let mut s = Store::create(&dir.0.join("books-data"), Currency::USD).unwrap();
+    s.add_account("1000", "Checking", AccountType::Asset, None, false)
+        .unwrap();
+    s.add_account("3000", "Capital", AccountType::Equity, None, false)
+        .unwrap();
+    let client = s.add_customer("Harbor Client").unwrap();
+    let inv = s
+        .create_invoice(
+            client,
+            d(2026, 2, 1),
+            d(2026, 3, 1),
+            vec![line("Consulting", 50_000)],
+        )
+        .unwrap();
+    let (entry, _) = s
+        .write_off_invoice(
+            inv,
+            d(2026, 3, 10),
+            Decimal::new(50_000, 2),
+            "collection exhausted",
+            Some(ledger_store::WriteOffEvidence::File {
+                file_name: "collection-letter.pdf",
+                mime_type: "application/pdf",
+                bytes: b"%PDF-1.4\nFinal demand\n%%EOF\n",
+                description: Some("Collection attempts"),
+            }),
+        )
+        .unwrap();
+    (inv, entry)
+}
+
+/// The write-off is on its invoice's timeline, reads "Written off", and
+/// opens its entry.
+#[test]
+fn a_write_off_shows_on_the_timeline() {
+    let dir = TempDir::new("write-off");
+    let (inv, entry) = write_off_books(&dir);
+    let mut h = open(&dir, Route::Invoice(inv));
+    shot(&mut h, "invoice-written-off");
+    assert!(
+        h.query_by_label_contains("Written off, entry #").is_some(),
+        "the timeline shows the write-off"
+    );
+    // The status chip reads its label ("Written off"), not "late".
+    assert!(h.query_by_label("Written off").is_some());
+    h.get_by_label_contains(&format!("Written off, entry #{entry},"))
+        .click();
+    h.run_steps(2);
+    assert_eq!(h.state_mut().route(), &Route::Entry(entry));
+}