Update Fulfillments: Split A Shopify Order After Its Add-Ons Have Shipped

Running Update Fulfillments on a Shopify order that had already fulfilled its add-on lines — shipping protection, carbon offsets, and similar non-physical items — errored out instead of reconciling against what was left, so any split, move, or merge spanning the add-on was blocked.

Update Fulfillments now plans against the quantities Shopify still shows outstanding, ignores lines with nothing remaining, and leaves already-shipped add-on lines alone. Two cases that used to give a generic failure now say what to do about them: a partial quantity spanning more than one Endless fulfillment, and Shopify having more remaining than Endless has planned. An unrelated hold on the order no longer blocks a valid plan.