commerce: reconciliation queries + federated-catalog stub (32 tests) — Phase 4 done

recon.sx — reconciliation as relational queries over the ledger: per-order
summary tuples + recon-statuso/neto/mismatcho miniKanren relations, so
overpaid/underpaid/settled and "settled to net N" are backward run* queries.
Tests cover double-charge guard, partial refund, webhook replay.

federation.sx (out-of-scope stub) — a federated catalog is the union of each
instance's product facts, so the same relations query cross-instance
(instances-with-sku, sku-offers, cheapest-offer). In-process mock, no network.

Completes the commerce-on-sx roadmap (Phases 1-4). Total 185/185 across 11 suites.

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

lib/commerce/scoreboard.md

@@ -13,4 +13,6 @@ _Generated by `lib/commerce/conformance.sh`_
 | quote | 13 | 0 | 13 |
 | ledger | 20 | 0 | 20 |
 | order | 21 | 0 | 21 |
-| **Total** | **153** | **0** | **153** |
+| recon | 20 | 0 | 20 |
+| federation | 12 | 0 | 12 |
+| **Total** | **185** | **0** | **185** |