The explicit Map assignment ran while the remainder was still parentless, so
splitting a container stack transiently registered it for decay only for
AddItem to unregister it one call later. Both AddItem overloads assign
Parent before Map, so the assignment was redundant for parented remainders;
keep it only for the ground case, where it places and enrolls the item.
The only code between the old assignment and AddItem is OnAfterDuped, and
no override reads the new item's Map.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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