feat(arap)!: documents read their figures from standing lines; control accounts

refuse hand entries (P4b S1, part A)

Plan P4b (D-45), slice S1, the engine half: rules.md B-38.

- ledger-core: every receivables or payables line carries its document
  (Ledger.line_docs: DocRef, Movement, DocTag), written by the document
  commands in the step that posts it, derived on replay from the existing
  document events (the role's account as it stood then; payments by the
  ordinal rule), copied onto a reversal's mirror. Ledger::stands_on;
  doc_state / invoice_state / bill_state (total, paid, outstanding,
  status Open/Partial/Paid/WrittenOff/Void, overdue days) as of any day;
  ar_aging / ap_aging read them, so reversed payments and voids are right.
  The control guard (add_line, add_line_fx, post_entry,
  register_recurring) refuses untagged lines on receivables/payables,
  exempting a reversal's mirror of a legacy line; replay never refuses.
  Bounds (kernel::running_bounds, bounds_kept) on payments and reversals;
  a document reversal never dated before its entry; deposit/payer accounts
  must be cash-like and hold no role. New API: receive_payment_with /
  pay_bill_with (PaymentDetails: instrument, reference), void_document /
  check_void_document, control_check, payments_recorded,
  standing_payments, replay_reverse_entry. Invoice.amount_paid/status
  remain only as derived caches for the MCP layer until part B.
  cashflow bill_splits reads payments from the tags.
- ledger-store: journal feature document_standing (D-39 gated) for a
  payment accepted only because an earlier one was reversed;
  receive_payment_with / pay_bill_with (instrument journaled as
  entry.instrument_set, reference in the description), void_document;
  replay uses replay_reverse_entry; schema 15 drops the projection's
  amount_paid/status. Fixture p4-arap-before + golden figures written by
  the version before S1, adjudicated in arap_standing.rs.
- ledger-gui: party card, cash "coming up" and company owed totals read
  doc_state as of today (late from the derived state).
- Lean Documents.lean (control_agrees and friends); Kani
  bounds_check_matches_definition,
bounds_kept_is_the_definition_on_books_in_bounds;
  rules B-38, B-18/B-23 amended; bookspec `older = true` for legacy hand
  lines; tests that hand-post to 1200/2000 post as replay or renumbered.

Review fixes (both reviews of part A):
- control_role_of guards only an account the role is assigned to or one
  holding its documents' lines (a chart's own 1200 Equipment or card at
  2000 is free until a document posts there); payment accounts check
  other roles by holds_role (type-checked). The MCP tests that failed on
  the guard (oracle_mcp, spec_projects) pass unchanged.
- standing_payments leaves out reversals (sorted, deduped); replayed
  tags match the movement's side; payments_recorded counts every payment
  event (tagged or not, Ledger.payment_events) and refuses overflow.
- The record caches settled (paid + discounted + written off) and owed
  (Invoice/Bill.owed, never serialized): a void never reads as paid.
- assign_role: receivables/payables refuse moving onto an account with
  untagged lines (RoleAccountHasHandLines) and, on their control account
  holding a balance, say DocumentRoleHoldsBalance (no hand entry named);
  B-23 reworded. The reversal-mirror exemption only takes a hand line
  off (even chain depth); putting it back is refused.
- DocStatus Overpaid and Unattached; aging leaves out credit balances;
  ControlCheck.attention lists out-of-bounds and unattached documents.
- stands_on counts a chain in order; indexes (doc_index, doc_accounts,
  order_pos, reversed_by) keep the derived figures linear.
- Viewer reads a post-dated document as of its own date; one state per
  row. bounds_kept's side-crossing documented as intended.
- Tests: ten new spec_documents scenarios, stronger proptests, store
  proptest arap_props (live = replay = snapshot at every date, closed
  months), fuzz ops void/payments with details, a GUI post-dated test;
  Lean Step.assign / Step.release with unattached_zero kept; model
  limits stated in docs/testing.md and B-38.
Review fixes (CPA and engineering lenses): only an assigned role's
account or one holding document lines is a control account (a chart's
own 1200 asset stays free); a role can't move onto untagged lines or off
document lines (Lean Step.assign); a void's cache never reads as paid;
no Decimal sum panics; per-document indexes keep figures linear; a
replayed tag matches its side; the feature gate counts payment events;
a payment's reversal is never listed as standing; an overpaid document
has its own status; the viewer keeps post-dated documents.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

crates/ledger-gui/src/books.rs

@@ -179,9 +179,10 @@ pub fn period_month(period: &str) -> Option<(i32, u32)> {
 ///   3. invoiced_ytd = Σ Invoice::total() over its customer record's
 ///      invoices dated in the year; billed_ytd the same for its vendor
 ///      record's bills.
-///   4. open_invoices = Σ Invoice::balance() over its customer record's
-///      invoices; open_bills = Σ Bill::balance() over its vendor record's
-///      bills (any date: what is still owed today).
+///   4. open_invoices = Σ what each of its customer record's invoices
+///      owes today (Books::owed_today: read from the ledger lines tagged
+///      with it, so a reversed payment or a void counts as it should,
+///      rules.md B-38); open_bills the same for its vendor record's bills.
 ///   4a. Each of 3 and 4 is None when it can't be summed exactly (a
 ///      document is restored as an earlier version journaled it, of any
 ///      size: rules.md B-28), never a wrong number.
@@ -1138,7 +1139,10 @@ impl Books {
                 .and_then(|p| out.get_mut(&p))
             {
                 info.invoices.push(id);
-                add(&mut info.open_invoices, inv.balance());
+                add(
+                    &mut info.open_invoices,
+                    self.owed_today(ledger_core::DocRef::Invoice(id)),
+                );
                 if in_year(inv.date) {
                     add(&mut info.invoiced_ytd, inv.total());
                 }
@@ -1151,7 +1155,10 @@ impl Books {
                 .and_then(|p| out.get_mut(&p))
             {
                 info.bills.push(id);
-                add(&mut info.open_bills, bill.balance());
+                add(
+                    &mut info.open_bills,
+                    self.owed_today(ledger_core::DocRef::Bill(id)),
+                );
                 if in_year(bill.date) {
                     add(&mut info.billed_ytd, bill.total());
                 }
@@ -1309,6 +1316,38 @@ impl Books {
             .collect()
     }
 
+    /// A document as of today: what it is, read from the ledger lines
+    /// tagged with it (ledger_core::Ledger::doc_state, rules.md B-38), the
+    /// figures books.ar_aging and books.party read. One dated after today
+    /// (a post-dated bill) is read as of its own date: what it will owe
+    /// when it is issued, so the forward-looking views keep it; it is
+    /// never late. `Ok(None)` only for an unknown document.
+    pub fn doc_today(
+        &self,
+        doc: ledger_core::DocRef,
+    ) -> Result<Option<ledger_core::DocState>, ledger_core::LedgerError> {
+        let date = match doc {
+            ledger_core::DocRef::Invoice(id) => self.ledger.get_invoice(id).map(|i| i.date),
+            ledger_core::DocRef::Bill(id) => self.ledger.get_bill(id).map(|b| b.date),
+        };
+        let Some(date) = date else {
+            return Ok(None);
+        };
+        self.ledger.doc_state(doc, self.today.max(date))
+    }
+
+    /// What a document owes today ([`Self::doc_today`]: one dated after
+    /// today, what it will owe on its date); refused when it can't be
+    /// computed (shown as such, never as a wrong number).
+    pub fn owed_today(
+        &self,
+        doc: ledger_core::DocRef,
+    ) -> Result<Decimal, ledger_core::LedgerError> {
+        Ok(self
+            .doc_today(doc)?
+            .map_or(Decimal::ZERO, |st| st.outstanding))
+    }
+
     /// The subjects whose documents an entry's page shows: the entry, and
     /// the invoice, bill, or payroll run it records (those have no page
     /// of their own).
@@ -2193,6 +2232,18 @@ fn disposal_true_up(
         .map_or(Decimal::ZERO, |t| t - runs)
 }
 
+/// What a document's state ([`Books::doc_today`]) says it owes, read once
+/// for both the row and its flags: `None` when it can't be computed
+/// (shown as such, never as a wrong number); nothing for an unknown one.
+pub fn owed_of(
+    state: &Result<Option<ledger_core::DocState>, ledger_core::LedgerError>,
+) -> Option<Decimal> {
+    match state {
+        Ok(st) => Some(st.map_or(Decimal::ZERO, |st| st.outstanding)),
+        Err(_) => None,
+    }
+}
+
 /// Entry ids a journal line refers to.
 pub fn entry_refs(line: &JournalLine) -> Vec<EntryId> {
     let p = &line.payload;