stock.sx — reservation as a precondition the host checks before order-begin!
(validate -> begin), keeping the flow pure. available-stock reads catalog stock
facts; can-reserve?/reserve-check/reservation-shortfalls gate a cart;
effective-available nets out concurrent reservations so orders can't
over-reserve; sufficient-stocko is the multidirectional availability query.
Total 258/258 across 16 suites.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>