commerce: provider-neutral payment-request envelope (8 tests) — Phase 5 ext

payment.sx — payment-request materialises {:order :amount :currency :return-url}
at the IO edge (amount from the ledger, currency/return-url host-supplied), so
lib/commerce stays vendor-agnostic; SumUp/Stripe adapters live in the orders
service and order-settle!(ref, amount) is the resume seam. pending-payments
enumerates suspended orders + envelopes (host poller seam). Gotcha handled: a
Scheme string flow-payload round-trips back wrapped as {:scm-string ...} —
unwrapped via scm->string. Total 209/209 across 13 suites.

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

plans/commerce-on-sx.md

@@ -21,7 +21,7 @@ reconciliation — all auditable via the event log.
 
 ## Status (rolling)
 
-`bash lib/commerce/conformance.sh` → **201/201** (12 suites; + attribution) — **roadmap complete; Phase 5 extensions in progress**
+`bash lib/commerce/conformance.sh` → **209/209** (13 suites; + payment) — **roadmap complete; Phase 5 extensions in progress**
 
 ## Ground rules
 
@@ -89,14 +89,23 @@ that unlocks the most tests per effort each iteration.
   flow-on-sx flow, recorded in the ledger; idempotent.
 - [ ] stock-constrained reservation — order-begin! fails (railway `fail`) when
   requested qty exceeds stocko availability; reservation decrements a stock view.
-- [ ] provider-neutral payment-request envelope — the `'payment` suspension carries
-  `{:order :amount :currency :return-url}` (mirroring flow `host.sx`'s `request`
-  envelope) so any provider's host adapter can initiate payment without the engine
-  knowing the vendor. SumUp/Stripe/etc. adapters stay at the IO edge (orders
-  service); `order-settle!(ref, amount)` remains the vendor-neutral resume seam.
-  Keeps lib/commerce provider-agnostic; enables multi-provider support in the core.
+- [x] provider-neutral payment-request envelope — `payment.sx`: `payment-request`
+  materialises `{:order :amount :currency :return-url}` at the IO edge (amount from
+  the ledger, currency/return-url host-supplied); `pending-payments` enumerates
+  suspended orders with their envelopes (host poller seam). Engine stays vendor-
+  agnostic; `order-settle!(ref, amount)` is the resume seam.
 
 ## Progress log
+- 2026-06-07 — `payment.sx` (Phase 5 ext, the item the user asked about):
+  provider-neutral payment-request envelope, materialised at the IO edge from the
+  ledger amount + host-supplied currency/return-url — keeps lib/commerce vendor-
+  agnostic (SumUp/Stripe adapters live in the orders service). `payment-request`
+  builds the `{:order :amount :currency :return-url}` envelope; `pending-payments`
+  is the host-poller seam listing suspended orders + their envelopes. Gotcha: a
+  Scheme **string** carried as a flow payload round-trips back to SX wrapped as
+  `{:scm-string "..."}` (numbers come back clean) — unwrap via `scm->string`
+  before using it as the oid. payment suite 7/7 + 1 order-suite integration test;
+  total 209/209 (13 suites).
 - 2026-06-07 — `attribution.sx` (Phase 5 ext): line-level discount attribution —
   the briefing's marquee "which line item triggered this discount?" query.
   `promo-lines` is the pure per-promo scope (percent/member → class lines, bundle