The control plane's seats grew a second naming style (the-*) beside mesh-*,
and the closed set was the only place any seat could be defined. This settles
both: system seats are mesh-* (one, mesh-wide) or node-* (one per node), named
for scope; a module may define its own seat outside the closed set. Folds in
the seat review: mesh-build-machine (scope fix), mesh-private-network (one
server + client modules, dropping per-node VPN choice), showcase becomes the
first module-defined seat, node-uplink, and the node-* renames — plus the
registry consolidation onto gitea, which reshapes the registry seats and gates
retiring distribution/verdaccio. Records why the renames are a coordinated
migration and why distribution cannot be removed until gitea serves images.
jschoubben