Balance your skills!
As a technical leader you have to align the technical direction and to lead your team. Therefore you need to build a set of balanced skills:
Architecture: You need to have a broader understanding of how all parts of the system work together. You need to know the deployment process and the management of the software in production mode.
Leadership: Mostly underestimated as a technical leader you need to have strong leadership skills like giving direction, influencing, delegation, encouragement and coaching.
Development: A technical leader has to master the art of coding - how to write, how to test, how to review. You have to know the tech stacks and modern frameworks.