Since the build CPU cap (issue 1806) shanks' mesh-build-go kept capacity 3 inside a 12-core slice:
three full checks got about 4 cores each and ran past the 30-minute step bound (issue 1890).
The puller now judges by min(configured, floor(slice quota cores / cores-per-step)), the quota
read live from its cgroup, says it on change and writes capacity.<node> to the pauses state.
A run's phases (fetch and merge, digest, tests) are logged with the ask id and written to its
running step key; Asker.Wait hands every step value to a WithStepSeen hook.