https://superuser.com/questions/187639/zsh-not-hitting-profile says zsh reads ~/.profile when run as sh, same as bash, so this seems sufficient to me.
~/.zprofile and ~/.bashrc have to source ~/.profile, that's always been true.
So we have to tell users that stuff like PATH should be setup in ~/.profile and that will work without having to introduce this, and it'll work with more than just Geany.
But ideally these should be setup user-wide.