v0.18.3

Fixed

• thread/pool: a Forward landing between a run's running receipt and its running mark — the run holding its slot, the ledger reading running, the pool's phase still queued — is refused as the state the run is leaving, accepted before a first run and parked before a resume, as Forward's godoc says; v0.18.2 fell through to the ledger and refused with a *StateError reading running ("receipt … is running, not running"), so a caller retrying only on accepted gave up before its steer landed (the arena's pool18.restart under full-suite load: its child then never saw the steer and its gated model looped on, Wait timing out — the hang was the scenario's, no delegation was left unsettled). A Forward while the child settles — the settled phase down, the settlement receipt not yet written — names the state it settles to instead of the ledger's running; one to a parked child is refused as parked even when a decision resumes it at that moment (the refusal was read from the ledger after the pool's lock was let go, the resume's running receipt already there). A refusal of a child this pool runs is now the state read under the pool's lock with its phase, the ledger read only for a receipt no child of this pool serves; Forward's godoc says such a refusal never reads running. TestForwardBetweenTheRunningReceiptAndTheMarkReadsTheStateItLeaves, TestForwardWhileSettlingReadsTheSettlement, TestForwardToAParkedChildResumingMeanwhileReadsParked, TestForwardWhileParkingNeverReadsRunning, TestForwardRetriedFromTheReceiptSteers (the arena's shape, failing on its first iteration on v0.18.2; POOL_FORWARD_RETRY_ITERS); TestNestedRandomChains retries a Forward at every Submit receipt from its creation until it steers on one iteration in three, before and after a restart (POOL_CHAINS_FORWARD_RETRY).