feat(mcp): the create tools preview and confirm, and the party keeps its contact block (P4b S4.4)

An invoice is issued, not edited. Without `confirmed` the create tools now
preview: the posting (with the accounts' codes, which the live chart may
not hold yet), the number it will take, its due date, terms and early
discount, warnings, and for an invoice the DRAFT copy of the PDF, handed
over as a file. Nothing is written and no number is used up. With
`confirmed` the invoice posts, takes the number the preview showed, and
files the issued copy with itself in the same call: `receipt.attached` on
its entry plus the link to the invoice, its SHA-256 in the event (A-1,
A-7, B-40). The copy the customer received is therefore the copy in the
books, and `books.document`'s re-created page can never be mistaken for
it. The result also carries a `mailto` link for a human to send it; the
books never send (A-4).

A bill keeps what the plan says a bill is: the vendor's own invoice
number, the vendor's invoice filed on its entry as its evidence, and, in
books that have declared `documents_v2`, an account on every line, so no
bill can land in General Expenses by default any more (A-9, A-10, A-13).
A vendor number entered twice is refused unless the caller says why, and
the reason is journaled with the second bill (B-40 item 4). Books that
have not declared the feature keep recording bills exactly as before, so
the owner's books keep working between units (D-39, 8.0.4).

Terms are resolved in one place and in one order: the due date given,
else the terms given, else the customer's or vendor's own default, else
the books' `invoicing.default_terms`; a document given only a due date
stores no terms, so an old-shape invoice is still written byte for byte
as before (B-39, A-13).

D-55: a party carries the owner's full contact block (phone, contact
person, billing and shipping addresses, billing email). It rides the same
`party.updated` event behind `documents_v2`, and an invoice's bill-to is
snapshotted at issue with the billing address and billing email in place
of the general ones when the party has them — `PartySnapshot::from_party`
is the one place that rule lives, so a later edit cannot change what was
sent, and the next invoice takes today's details.

Tests: the wire tests are the new `crates/ledger-cli/tests/documents.rs`
(preview writes nothing, the DRAFT copy, the issued copy's SHA-256 equals
`books.get_receipt`'s, numbers run, a bill's file and terms, the duplicate
refusal, the line-account rules, the terms fallback, the `party_id` alias
and the ambiguity it refuses, the contact block's set and clear, and the
bill-to at issue); `format_upgrade.rs` gains
`documents_v2_refused_until_consent` and the cut-over test now refuses and
then makes a document carrying a new field (8.0.6 item 3); the store
tests are `the_contact_block_round_trips_and_replays` and
`an_invoice_keeps_the_billing_details_it_was_issued_with`, and
`books_written_under_older_rules_still_open` gains a hand-written
contact-block event (8.0.6 item 1).

Merge does not need the owner's go-ahead: the live books refuse a write
that needs `documents_v2` until he gives it, and take every other write as
before (8.0.6 item 6). No figure moved: S4 moves none.

crates/ledger-cli/tests/format_upgrade.rs

@@ -611,6 +611,63 @@ fn format_upgrade_waits_for_consent() {
     assert_eq!(format_lines(&dir), 1);
 }
 
+/// plan P4b S4.4 (R-A step 4, 8.0.6 item 3): on books that haven't
+/// declared `documents_v2`, an invoice carrying a new field (terms) is
+/// refused with the upgrade remedy and journals nothing, while one
+/// carrying none posts as before; after the owner's go-ahead the same call
+/// is made, and takes the first number.
+#[test]
+fn documents_v2_refused_until_consent() {
+    let home = Home::new("documents-v2");
+    let dir = old_books(&home, "acme");
+    let _held = serve(&home);
+    let out = home
+        .cmd("token")
+        .args(["create", "--book", "acme"])
+        .stdin(Stdio::null())
+        .output()
+        .unwrap();
+    assert!(out.status.success(), "{out:?}");
+    let mut a = Agent::start(&home, "acme");
+    let customer = a
+        .call("books.add_customer", json!({"name": "Harbor Coffee"}))
+        .unwrap()["id"]
+        .clone();
+    let line = json!([{"description": "Design", "amount": "500.00"}]);
+    let with_terms = json!({"customer": customer.to_string(), "date": "2026-02-10",
+                            "terms": "Net 30", "lines": line, "confirmed": true});
+    let before = journal(&dir);
+    let refused = a
+        .call("books.create_invoice", with_terms.clone())
+        .unwrap_err();
+    assert!(refused.starts_with("format_upgrade_pending"), "{refused}");
+    assert!(refused.contains("documents_v2"), "{refused}");
+    assert_eq!(journal(&dir), before, "a refusal journals nothing");
+    // A document carrying none of the new fields posts as before, and
+    // files its copy; it takes no number (an older version reads it).
+    let plain = a
+        .call(
+            "books.create_invoice",
+            json!({"customer": customer.to_string(), "date": "2026-02-10", "due_date": "2026-03-12",
+                   "lines": line, "confirmed": true}),
+        )
+        .unwrap();
+    assert!(plain.get("number").is_none(), "{plain}");
+    assert_eq!(plain["total"], "500.00");
+
+    // The go-ahead.
+    let mut words = home.words("books");
+    words.extend(["upgrade".into(), "acme".into()]);
+    let (code, shown) = home.at_terminal(&words, &[PASS]);
+    assert_eq!(code, 0, "{shown}");
+    assert_eq!(format_lines(&dir), 1, "the format moved once");
+    let made = a.call("books.create_invoice", with_terms).unwrap();
+    assert_eq!(made["number"], "INV-0001", "{made}");
+    assert_eq!(made["terms"], "Net 30", "{made}");
+    assert_eq!(made["due_date"], "2026-03-12", "{made}");
+    a.call("books.verify", json!({})).unwrap();
+}
+
 /// Copy the tree `from` into `to`, private as the server keeps a book
 /// (folders 0700, files 0600).
 fn copy_private(from: &Path, to: &Path) {
@@ -705,17 +762,24 @@ fn books_p2_served_cut_over_whole() {
         .unwrap();
     let waiting = journal(&dir);
     let refused: Vec<(&str, Value)> = vec![
-        // An invoice's or bill's line naming its project
-        // (document_line_projects, rules.md B-37 item 8).
+        // An invoice carrying documents_v2's fields (terms: P4b S4.4) and
+        // its line naming its project (document_line_projects, rules.md
+        // B-37 item 8).
         (
             "books.create_invoice",
-            json!({"party_id": 1, "date": "2026-02-10", "due_date": "2026-03-12",
-                   "lines": [{"description": "Design", "amount": "500.00", "class": "Lighthouse"}]}),
+            json!({"customer": "1", "date": "2026-02-10", "terms": "Net 30",
+                   "lines": [{"description": "Design", "amount": "500.00", "class": "Lighthouse"}],
+                   "confirmed": true}),
         ),
+        // A bill carrying documents_v2's fields (the vendor's number, the
+        // line's account, its invoice: A-10, A-13) and its line's project.
         (
             "books.create_bill",
-            json!({"party_id": 1, "date": "2026-02-11", "due_date": "2026-03-13",
-                   "lines": [{"description": "Drafting", "amount": "120.00", "class": "Lighthouse"}]}),
+            json!({"vendor": "1", "date": "2026-02-11", "due_date": "2026-03-13",
+                   "vendor_ref": "L-77",
+                   "lines": [{"description": "Drafting", "amount": "120.00",
+                              "account": "6600", "class": "Lighthouse"}],
+                   "existing_attachment_id": 1, "confirmed": true}),
         ),
         (
             "books.set_setting",