commerce: order ledger on persist + idempotent reconciliation (20 tests)

ledger.sx — each order is an append-only persist stream "order/<id>";
status/total/paid/recon are folds over events (ledger = source of truth).
order-pay / order-refund are idempotent via persist/append-once keyed on the
payment ref, so a replayed SumUp webhook records once. order-recon-of
classifies unpaid/ok/underpaid/overpaid on net vs total; ledger-mismatches
finds genuine paid != ordered across streams. minikanren+scheme/flow+persist
verified coexisting in one process. Total 132/132 across 8 suites.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/commerce/scoreboard.json

@@ -6,9 +6,10 @@
     "api": {"pass": 12, "fail": 0},
     "promo": {"pass": 17, "fail": 0},
     "stack": {"pass": 16, "fail": 0},
-    "quote": {"pass": 13, "fail": 0}
+    "quote": {"pass": 13, "fail": 0},
+    "ledger": {"pass": 20, "fail": 0}
   },
-  "total_pass": 112,
+  "total_pass": 132,
   "total_fail": 0,
-  "total": 112
+  "total": 132
 }