Library not loaded: /usr/local/opt/readline/lib/libreadline.7.dylib
This was a horrible way to spend a Friday afternoon. At some point, I installed something via Homebrew that borked/updated readline.
I still do not understand the issue 100%, but my best guess is ruby gems with native extensions were failing because of the dependency change. How it happened? Computers!
Re-installing Ruby (rbenv install ruby_version) seems to have addressed most of the issues (also needed to update bootstap to a newer version).
Wish I had a better recommendation for how to fix it and why it worked, but hopefully this is start for others.