stepAll

Step every queued eval once, in order, under ONE timeout budget for this tick: they run serially on this one tick thread, so their combined time is what would freeze it. The guard inlined into each script reads this lane's kill-id field, which beginFrame's watchdog writes when the budget elapses (see TimeoutGuard). Drains to empty, so an eval that finishes compiling mid-pump runs this tick instead of waiting out a heartbeat.

Whatever this loop polls is epoch-current: offerOrReap is the only door into active and refuses a stale task, and currentEpoch's sole writer (reapOnStop) runs on this thread outside any pump.