Announce (theta-gateway) + discover/apply/revert (theta-agent) confirmed
working end-to-end over real multicast between real containers, including
two real bugs found and fixed along the way (IPv6 query abort, EBUSY on
rename over a bind-mounted /etc/hosts).
Windows/macOS mDNS is now the ONLY unbuilt piece of the original design
this session set out to implement -- and it's blocked on platform access
this environment doesn't have, not on missing design or effort.