A module serves tools under an account scoped to exactly that, and nothing else in
the mesh held an account that could ask one. The control plane does: ask publishes
on the RPC exchange with a private reply queue bound under its own name, checks the
correlation, prints the answer, and exits non-zero for a tool that answered with an
error or a module that never answered (novox/hq 04-ISSUES/049, ADR 0095).
