Friend took my startup idea and is now letting me know he build it and is going to sell it. I will not promote

2 years ago I started building a tech startup and confided in my friend about the progress. Though it was a promising idea, it involved some AI tech which was a bit too expensive at the time in order for it to be profitable. I wrapped up the tech project, 95% done and went on with my life. Well, now with AI progress speeding up I realized that it could be profitable now and I should wrap it up though I didn't get to it yet because of other personal issues. I was surprised when my friend told me what side project they started vibe coding and I got demoed a full working version, though still less advanced than the one I built. He then told me of his plans to sell it in the industry we both activate in, as it's a niche project. He also started confiding in me with regards to issues he's facing and thought provoking me . A part of me wants to ask him to collaborate and go ahead together, but now sure if I could trust him any longer and either way both versions of the startup are 85% done at least, though he wants it to make it a full saas, so arguably there's still room to grow. I'm not sure why did he warn me he finished it in the first place, perhaps so I can advise him with issues he's facing or to salvage the friendship. How would you deal with this situation? I can wrap up my project as well in 2 weeks time, though the aftermath will be ugly as everyone in the industry sees us as friends and both coming up with almost identical startups will look strange.