[paymog]

Summary

R.tick now records each attempt's outcome when that attempt finishes, gives its pool unit back, and starts the next due ticket in that unit. Before, one slow job held the whole round: the other units sat idle until it ended.

Design decisions

• One outcome channel per round. Each attempt sends (ticket id, outcome) on a shared channel, as IO.within does in Base. The loop receives whichever answers first. Before, the loop joined per-attempt channels in list order.
• Write-ahead order is unchanged. Each settle still appends Complete/Requeue before it changes the state and releases the grant. The next Select comes after that.
• Fuel bound. The round's claim fuel (1 + pending at tick start) is shared by every refill, and an idle pick gives its unit back. Each attempt settles once, so the loop's settle fuel never runs out before the last attempt ends.
• Breaker check moved to threshold 1. Outcomes now reach the breaker as they arrive. With threshold 2 and retry-after 0, the first failed job is due again before the second failure is recorded, so a third attempt is correct behavior. At threshold 1 the check keeps its intent: two jobs fail at once, and no third attempt starts.
• Flight loses its chan field, so runner goes to 0.5.0.0. Nothing imports runner from the hub yet.

Validation

• New check.bend scenario: capacity 2, one 1 s job, and five fast jobs. One tick runs all six. At most 2 attempts overlap in the job log, and the slow job's end is the last line. Against the old tick, this check fails: one round ran only 2 of the 6 jobs.
• pick_bounded and pick_release still cover each claim's pool step. The log check covers the loop end to end.
• scripts/check.sh runner passes, including the crash, compaction, and webhook scenarios. scripts/publish.sh --check passes.

Closes #443