mesh/merge-gate pass: builds build-agent, mesh-controller, route-proxy → ace, g14, novox, shanks; no bus step; every machine composes with the change as it…
The witness moves a running build aside into a directory the controller's user
cannot enter, then deletes it; a verb exec'd from os.Executable() in that window
failed with permission denied. /proc/self/exe stays valid while the process lives.
A verb that still cannot start, or arrives while the controller stops, is refused
with link.ErrHandingOver and marked retry: handing-over.
