private/delete_subaccount

Permanently deletes one of the caller's subaccounts via a signed action. The subaccount must be fully wound down: no balances or debt, no open orders, RFQs, or quotes, not a vault, not under auction, and not the wallet's fallback subaccount. Deletion never moves value; subaccount ids are never reused. This is an owner-or-admin operation (session keys need the admin scope).