Default login shell is now bash for all hosts; interactive bash
sessions exec into nushell via /etc/bashrc. A ~/.bashrc sourcing
/etc/bashrc covers non-login interactive shells (terminal emulators).
Non-interactive SSH exec (mosh app bootstrap, scripts) keeps POSIX
shell semantics. Reverts the kratos-host-specific overlay from
765ae15.
The old Android Mosh app discovers mosh-server via POSIX shell idioms
(command -v / type) through the user's login shell. Nushell has no
command/type builtins and which prints a table, so the app reported
'mosh-server Not Found' on kratos (user shell: nu) while working on
hermes (app logs in as bash user).
Fix: use bash as login shell on kratos and exec into nushell for
interactive login sessions via programs.bash.interactiveShellInit.
Non-interactive SSH exec (app bootstrap, Termux mosh) stays in bash
where POSIX semantics work.
Also fixes the stale nh flake path (p/nixos -> p/NIX).
m3ta-chiron
m3tm3re