Delete Subaccount

Delete a subaccount. Custodial subaccounts cannot be deleted.

Refused with 409 if the subaccount has any open order (resting/in-flight orders, or an active iceberg, peg, smart-taker or conditional order) — cancel those first.

This is a soft delete: the row is marked is_active = false so the audit trail (orders, fills, ledger entries) stays intact. The user never sees it again.