Soft-delete several product lines, none of which may ever have been used.

All or nothing, which is the single-row rule applied to a selection rather than a second one: removing the rest of a selection the caller confirmed as a whole would take out more than they can see they asked for. The list already carries each row's usage, so the UI can refuse before the request; this catches the selection whose counts went stale.

The rows are retained and stop appearing anywhere a product line is listed or picked, so deleting the same selection twice is a 404 rather than a second delete.