Orders: Sales Channel Now Locked To The Order's Own Company

An order can no longer end up carrying a sales channel from another company. A channel belonging to a different company was showing up on some orders, and the cause was two write paths letting a wrong-company channel slip through: order create/update was keeping per-request state on shared instances that leaked between concurrent requests, and the sales-channel automation action never checked the channel's owner. Both paths now scope the channel to the order's company and reject a channel from anywhere else. Already-affected orders will be corrected in a separate cleanup.