pacman-rc.conf shipped with [omarchy] on pkgs.omarchy.org/edge — a
leftover from when release candidates published there. Candidates now
publish to a dedicated rc channel, so a machine switched to rc with
omarchy-refresh-pacman was pairing the rc Arch mirror with edge omarchy
packages, and omarchy-version-channel could not name the rc repository
at all (an rc install reported 'rc / unknown').
Point the conf at pkgs.omarchy.org/rc, teach omarchy-version-channel
the rc repository, and repoint existing rc-channel machines with a
migration. The migration only rewrites the shipped pairing (rc mirror +
edge [omarchy]); an administrator's deliberate combination is kept.