In order to support a desktop-native VPN connection to Coder, we need to migrate away from the IPv6 prefix we know is already in use by Tailscale, otherwise we cannot work on a system where Tailscale is also enabled (this doesn't matter today since networking is entirely in-process).

Our new prefix isfd60:627a:a42b::/48 which is aUnique Local Address prefix, randomly chosen.

Agents should useboth the new prefix and the old Tailscale prefix for the time being, to avoid incompatibility with existing clients.