ControlService
CLI → local daemon.
RequestJoin
Signature: RequestJoin(RequestJoinRequest) returns (RequestJoinResponse)
Request: addr (existing member Runtime API), token, optional observer.
Response: joined, message, members, cert_issued.
RequestPromote
Signature: RequestPromote(RequestPromoteRequest) returns (RequestPromoteResponse)
Request: optional node_id (empty = local node).
Response: promoted, message, members. Unknown id → NotFound. Already a voter → promoted = true.