Interesting. I was just thinking, do the CTO and the CEO know each other from before? Was it the CEOs idea to hire this CTO maybe? If that's the case maybe this was planned between the CTO and CEO.

Since you're the founder with the focus on the tech aspect (basically you should be the CTO) what was the reason for hiring the CTO in the first place? A CTO that's obviously not a better software developer than you. Hard facts, but maybe it was your partner who planned this since the very beginning.

After you've talked to your lawyer you could possibly strike a deal with the CTO / CEO and go become an employee if you are interested in just keeping on coding for the company. Maybe getting a bonus that if you decide to leave or still be on the companies payroll provided that the company reach a certain revenue / value etc.