atom, atom-beta: 1.27.0 -> 1.27.1, 1.24.0-beta3 -> 1.28.0-beta1

Also rewrote the derivation for easier maintencence.

(And added @ysndr as maintainer for atom-beta, kind of an implicit
result of joining the two. If you're not okay with that, I'll patch
you out, but I'll presume consent.)