commerce: time-windowed promotions (19 tests) — Phase 5 ext

window.sx — a validity window kept separate from the promo tuple (promo.sx
untouched): windowed promo (promo from until), inclusive int timestamps, nil =
open bound. active-ruleset filters to promos live at `at` and feeds the existing
promo/stack/quote pipeline; active-codes is the backward "which codes live at
T?" query; windowed-quote is the datetime-aware, deterministic quote.
Total 228/228 across 14 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` → **209/209** (13 suites; + payment) — **roadmap complete; Phase 5 extensions in progress**
+`bash lib/commerce/conformance.sh` → **228/228** (14 suites; + window) — **roadmap complete; Phase 5 extensions in progress**
 
 ## Ground rules
 
@@ -81,8 +81,9 @@ that unlocks the most tests per effort each iteration.
 - [x] line-level discount attribution — "which line item triggered this discount?"
   as a backward miniKanren query (`attribution.sx`: `promo-toucheso` relation,
   `lines-for-code`/`codes-for-line` both directions, `order-level-codes` for fixed).
-- [ ] time-windowed promotions — promos gated by a validity window; quote takes a
-  datetime, determinism preserved. (quote.sx already documents datetime intent.)
+- [x] time-windowed promotions — `window.sx`: windowed promo `(promo from until)`,
+  `active-ruleset`/`active-codes`/`windowed-quote` gate by datetime; feeds the
+  existing promo/stack/quote pipeline unchanged. Determinism preserved.
 - [ ] discount-aware tax policy — alternative `cart-quote` computing tax on the
   net (post-discount) base via proportional class allocation; explicit + tested.
 - [ ] refund as a flow — refund lifecycle (request → approve → settle) as a second
@@ -96,6 +97,13 @@ that unlocks the most tests per effort each iteration.
   agnostic; `order-settle!(ref, amount)` is the resume seam.
 
 ## Progress log
+- 2026-06-07 — `window.sx` (Phase 5 ext): time-windowed promotions. A validity
+  window is kept SEPARATE from the promo tuple — windowed promo `(promo from
+  until)` (inclusive int timestamps, nil = open bound). `active-ruleset` filters
+  to the plain promos live at `at` and feeds the existing promo/stack/quote
+  pipeline unchanged (promo.sx untouched); `active-promoo`/`active-codes` is the
+  backward "which codes are live at T?" query; `windowed-quote` is the
+  datetime-aware quote (deterministic in `at`). window suite 19/19; total 228/228.
 - 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-