The first live plan took seventy-five modules along for a controller change: the builder packages the
controller's source, everything is built by the builder, so everything was reachable. A module built by
the build machine is not changed by a new build machine. Reachability now follows the code and build
edges only; built-by still orders a tier after the build machine and gates it on the machine's roll-out.
plans stop <id> ends a plan by hand: what was asked still builds and registers, nothing further is asked.