Omnix fails to parse `nix --version`

`om ci`: flake check should be disabled by default

`om health` doesn't recognize official installer (macOS)

`om ci run` broken all of a sudden

[Feat]: Add option to `om ci` for selective package builds

`om develop`: Support `attic`

`om health` shows false negative against DetSys graphical installer

`om develop`: Don't use GitHub for omnixrc

Graceful shutdown

Nix flakes are not enabled for determinate installer