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/scoreboard.json

@@ -12,9 +12,10 @@
     "recon": {"pass": 20, "fail": 0},
     "federation": {"pass": 12, "fail": 0},
     "attribution": {"pass": 16, "fail": 0},
-    "payment": {"pass": 7, "fail": 0}
+    "payment": {"pass": 7, "fail": 0},
+    "window": {"pass": 19, "fail": 0}
   },
-  "total_pass": 209,
+  "total_pass": 228,
   "total_fail": 0,
-  "total": 209
+  "total": 228
 }