internal/netaddr parses a daemon seam address and dials or binds it. A
scheme-less address is unix and behaves exactly as it does today: same
0700 parent dir, same 0600 socket, same bytes on the wire. tcp://host:port
is the new option, and it is what lets a module live on another host.
Over tcp the filesystem permission that authenticated the unix socket is
gone, and what crosses this seam is audio of the owner speaking. So a tcp
listener requires a shared token, checked in constant time before the
first protocol frame is read, and a peer that fails is dropped without
taking the listener down with it.
