std/benchmarking — in-process timed benchmark harness. Drives a body through the effect-branch engine for a wall-clock duration, then reports the iteration count and the measured nanoseconds. Like hyperfine's timed runs, but in-process and zero-overhead: the `! pass` effect fires once per iteration until `seconds` elapse; `| done` carries the pass count and elapsed time. The drag-race protocol is `run(seconds: 5)` with the sieve in the `! pass` body, then emit the result.

~pub tor run { seconds: i64 }
! pass
| done { passes: i64, seconds: f64 }