there isn't a hook for executing shell source, but it would be possible to add I think. The current hooks already execute inside of a shell function so there would just need to be a way to declare that you want a hook to run inside the shell, maybe like this:

    [hooks.enter]
    shell = true
    run = ". completions/mycli.sh"

I made an issue if you'd like to track: https://github.com/jdx/mise/issues/3412