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-cli/tests/spec_mcp.rs

@@ -914,6 +914,21 @@ fn happy_path(name: &str) -> Mcp {
                "by": "Avery Quill", "recipients": ["billing@client.example"],
                "reference": "msg-1"}),
     );
+    // P4b S7: a bad debt, its evidence uploaded and filed with it.
+    let bad = m.ok(
+        "books.create_invoice",
+        json!({"party_id": customer, "date": "2026-02-03", "due_date": "2026-03-03",
+               "lines": [{"description": "Consulting, never paid", "amount": "400.00"}],
+               "confirmed": true}),
+    )["id"]
+        .as_u64()
+        .unwrap();
+    let letter = m.upload(b"Final demand", "letter.txt", "text/plain", "document");
+    m.ok(
+        "books.write_off_invoice",
+        json!({"invoice": bad, "date": "2026-03-01", "reason": "collection exhausted",
+               "upload_id": letter, "confirmed": true}),
+    );
 
     // Fixed assets.
     let registered = m.ok(