services.hyperhive.swarmName becomes services.hyperhive.swarm.name, with
one mkRenamedOptionModule in hyperhive.nix -- the module that declares
it, same convention as the forge and matrix renames, so each migration
stays independent of its siblings.
hiveName deliberately stays where it is. It names this hive; swarm.name
names the group the hive belongs to, and that they now sit one level
apart is the distinction rather than an inconsistency.
The per-agent hyperhive.swarmName is an internal mirror rendered from
the host value and does not move, same split as forge and matrix.
