Did you look much into Emacs and its huge variety of packages?
Edited to add: it's built with a vast amount of Lisp and so much of the application can be live modified at runtime via Lisp. If you want an extensible editor, you can learn a lot from Emacs.
Thanks for this! I've personally never used Emacs but I'm definitely taking a look now. A wild idea we have is to make the interface between AI and dev tools extensible, because we can't potentially build a fine-tuned integration for the full world of developer tools. But if developers are interested and they see the benefit of getting AI to handle these tools for them, they can probably work on implementing the interface and let AI take over.
(I'm sorry about the usage of AI so many times haha. I've been staying away from saying LLMs because they're the state-of-the-art today, but that potentially changes as soon as next year)
Edited to add: it's built with a vast amount of Lisp and so much of the application can be live modified at runtime via Lisp. If you want an extensible editor, you can learn a lot from Emacs.