Give Pi[1] a try. Comes pretty barebones out of the box, yet still provides a decent default experience. Extension points are all TypeScript if you want. There are a lot of examples[2] and some 3rd party extensions[3].
I'll point out that if you want permission prompts for certain behavior, you have to add that yourself. There's at least one example.
Edit: Just noticed the article's author is using a fork of Pi.
[1]: https://shittycodingagent.ai/
[2]: https://github.com/badlogic/pi-mono/tree/main/packages/codin...