// Package buildrun holds the parts every module that runs steps on the build modules shares: the caller, the steps
// watch and the runner of a long step (ADR 0469), the sets of presence, toolchains and healthy build modules, the
// places a node offers by capacity, and the choice of build nodes (ADR 0478). The builder and the checker of the
// delivery use them; they moved here from the builder's own package so neither keeps a copy (issue 1671, ADR 0484).
package buildrun