It's definitely possible to write code without AI. It's not that hard to turn off for a project. I use VS Code for a lot of my projects and there are options in the settings to turn off Auto Suggestion or Copilot. You could do it temporarily.
A program that I have been in love with is Micro that runs in the terminal. It's a lot easier and more accessible than nano (the default text editor that opens up when you edit files in the terminal) and way more accessible than vim/neovim. It has normal ctrl+s, ctrl-c, ctrl-v, etc functionality. You can use the mouse to select text, and it looks quite pretty. It also comes built in with syntax highlighting and code styling for programming languages. I've been using it more than VS Code actually (and about as much as Obsidian for note taking). It's way easier to not get distracted by a million plugins or other things lol.
I'm a participant and not helping run the challenge or anything, but I would assume most people would frown on having AI assistance somewhat. Though I may be wrong. I like using AI for prototyping or even generating things for me sometimes. Thing is with AI you can have a roguelike finish in less than 7 hours. I've had Claude and chatGPT generate some for me that are not even that bad. Usually for picking apart pieces and learning.
I feel the challenge is for people that can are making their own roguelike. Seems it would defeat the purpose if you vibe coded a roguelike for this challenge or had something else do the heavy lifting. But like I said I don't know and I read nothing explicit in the rules. I know that I'm not going to. It's not a gam jam contest so much as a personal challenge to see if we can. That is how I'm taking it. It's a challenge for me as a developer to see what I can accomplish. I'm learning as much as I can and playing a ton of roguelikes to get ready. I'm mean I'm always playing roguelikes but I'm devoting more time than usual.
I've only done the tcod tutorial so far and I'm not even sure if I'll be able to finish anything. Anyway, that's just my rant-y opinion.