Subscribe(pattern, handler) asks the runtime for the module's events and answers each mesh/event
only after the matching handlers returned nil, so the runtime acknowledges it on the bus then and
not before; Ask(key, body) calls a tool as the module. Topic matching is the TypeScript SDK's.
What the TypeScript SDK's stdio loop does, in Go: an empty name serves as MESH_SERVED_MODULE; each
call runs beside the loop so a tool waiting on the runtime does not deadlock it; Emit asks the
runtime (mesh/publish) with the same envelope and headers. README says how to install it and how
releases are tagged.