Catch-all zone

The catch-all zone is the shipping zone that covers every country not listed in another zone. Exactly one exists, it cannot be deleted, and its purpose is structural: no order can ever be unpriced because its destination was not in the rate card.

Merchant-defined zones are resolved first match, so an order to a country nobody listed would otherwise have no shipping rate at all. Rather than pricing it at zero, which quietly flatters the margin, it falls to the catch-all and the country is flagged so the gap can be closed deliberately.

Assigning a country to a zone removes it from the zone it was in, because a destination can only be in one zone at a time. That mutual exclusivity is what keeps the resolution unambiguous and the rate card readable.

The flag is the part worth acting on. A country repeatedly resolving to the catch-all is either a market worth pricing properly or one worth not shipping to, and both decisions are better made from data than from a shipping bill.