Confirmed the core idea (master terminates a connection, relays over a
spoke's WG mesh IP to a spoke with zero published/inbound ports of its
own) with a standalone test: an external client hit the master's public
port and got a response that could only have come from the spoke,
which had no reachable port except over the tunnel.
Deliberately did NOT wire this into theta-proxy's actual Lua/Redis
routing engine -- that needs its own dedicated pass to do safely, plus a
real service-to-service credential between sso-manager-node and
theta-proxy/theta-gateway that doesn't exist yet. Recorded as verified
mechanism / unbuilt automation, not conflated with either "done" or
"unknown whether it would even work."