attempts verifiedimportant

An attempt is counted when it begins, and its outcome lands in a later second. The console is explicit about the consequence in a comment of its own: rates are not computed against attempts, because the attempts of this second have not produced results yet. That matters for us directly. Our own reporting has been bitten by the same shape before — send_rollups.sent counts what was handed over, including messages that were later deferred, so a rate computed against it is not a rate of anything. The same discipline applies here: use deliveries + failures as the denominator, and keep attempts as a measure of effort rather than of outcome.