Audit fixes: party money, reconciliations, require policy, K-1 property

An independent recompute of the real books found no numeric
disagreements; review found 15 defects, all fixed with spec-first
regression tests:

- k1: a prepaid credited straight to capital is property; a member
  paying a vendor through 2100 is cash. Docs and B-13 match.
- parties: a reversal of a reversal counts on its root's side;
  liability-to-liability payments (member pays the card) count as paid.
- viewer: party money uses the server's cash accounts and full calendar
  year; per-party "What for" scales multi-party entries.
- reconciliations: refuse a withdrawn statement before journaling; new
  books.void_statement; reconciled lines can't be un-cleared; one shared
  reconcilable-accounts rule for digest and viewer.
- CPA package includes receipts linked to entries; a file can't be both
  filed on and linked to one entry.
- parties = "require" covers payroll, tax remittance (agency) and
  disposal (buyer); no-party marks follow reversal chains and clear when
  a vendor is tagged.
- derived member shares are frozen to exact amounts when posted, so a
  settings change never re-splits history.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX

crates/ledger-mcp/tests/spec_mcp.rs

@@ -997,6 +997,11 @@ fn happy_path(name: &str) -> Mcp {
         "books.void_reconciliation",
         json!({"reconciliation_id": rec, "reason": "redo after the March import"}),
     );
+    // Voided, its statement can be voided too, to record it again.
+    m.ok(
+        "books.void_statement",
+        json!({"attachment_id": stmt, "reason": "closing balance mistyped"}),
+    );
 
     // Periods.
     let p = m.ok(