Function settleStep

Run one bounded settlement phase on this queue and return the phase the queue is in afterwards, which the next call runs (phase_drain, phase_pay, or phase_done). Permissionless; aborts EMarketNotExpired before expiry.

• DRAIN, while unfinished orders remain: refund them in τ order with reason 5, visiting at most the policy's settle_refund_batch records, refunded or not. No pruning and no account rows, so each refund loads its record alone. A refund the receive address cannot take is parked in its record. Runs before and after Predict settles, and while Predict is frozen.
• PAY, once nothing is unfinished and Predict has settled the market: from the payout cursor, visit at most settle_payout_batch records. Each Open record is paid its settled payout through try_pay_settled (zero for a loser), marked Closed, and reported with OpenRecordSettled. A record the market cannot pay, or whose receive address is denied, stays Open with OpenRecordPayoutSkipped, and pay_open pays it later. Before Predict settles, a PAY call changes nothing.
• DONE: the call whose walk reaches the last record emits MarketPayoutsCompleted; later calls change nothing. Skipped records are still paid through pay_open.

The keeper sends one call per transaction until it returns phase_done().