You really don't have to accept contributions if the repo is open. You could simply disable issues and close all PRs with a comment explaining that you're not ready for contributions yet. You could even automate that with a Github Action or similar.

Developing in the open would make it easier to trust that you're not doing something nefarious. When I think about the kind of data that goes through my terminal on a day-to-day basis, I have to _know_ for sure that my terminal can be trusted. That makes Warp a non-starter for me until it's open source, which is really a shame because it looks fantastic.