The control/ns1/ns2 mesh IPs and the /88 subnet were duplicated literals in
mesh-hosts.nix. clan-core's zerotier generator already writes each machine's IP
as a public var (vars/per-machine/<m>/zerotier/zerotier-ip), so read from there
and derive the subnet from zerotier-network-id. Pure refactor: the rendered
values are identical and the system derivation hash is unchanged.
Berwn
848c4ec47d