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>

lib/commerce/conformance.sh

@@ -17,7 +17,7 @@ if [ ! -x "$SX_SERVER" ]; then
   exit 1
 fi
 
-SUITES=(catalog cart price api promo stack quote ledger order recon federation attribution payment)
+SUITES=(catalog cart price api promo stack quote ledger order recon federation attribution payment window)
 
 OUT_JSON="lib/commerce/scoreboard.json"
 OUT_MD="lib/commerce/scoreboard.md"
@@ -66,6 +66,7 @@ run_suite() {
 (load "lib/commerce/promo.sx")
 (load "lib/commerce/stack.sx")
 (load "lib/commerce/quote.sx")
+(load "lib/commerce/window.sx")
 (load "lib/commerce/ledger.sx")
 (load "lib/commerce/order.sx")
 (load "lib/commerce/payment.sx")