Technical and business co-founders - responsibilities I WILL NOT PROMOTE

Hi all! I pared up with business cofounder with an idea (I’m a tech cofounder). We refined an idea, I did competitor research, we found a market gap and they prepared a brand bible kind of stuff. Now we’re at the stage where we want to build simple prototype and start validation. And I’m getting nervous, I love software, building and talking to actual users like I do in my day job as a software engineer. I HATE selling, cold approaching and marketing. They expect me to validate market with them, go to relevant places and approach potential users to talk to them ect. I would rather setup waitlist page ans build clickable figma prototype. They want to work on figma together. In your experience in early stage startups, is this what technical co founders do? How did you divide responsibilities? Who did what when validating? How did you split equity?