Function setOrderFlow

Allowlist (enabled = true) or remove the witness type W of an order-flow companion for Predict's order-flow primitives. Removing it stops admissions, commits, and fills only: release and try_pay_settled need a receipt, not the allowlist, so waiting orders still drain and queue-held positions are still paid. Admin-only. Enabling is version-gated, since it grants authority; removing is ungated, like remove_flush_operator, so it works under the emergency freeze and from a package version below the runtime floor. Setting the state W already has changes nothing but still emits OrderFlowUpdated.