This is YC-style office hours in two modes: startup mode hits you with six forcing questions to expose demand reality and find your narrowest wedge, while builder mode is looser brainstorming for side projects and hackathons. It triggers on phrases like "is this worth building" or "help me think through this" and writes a design doc when you're done. The gbrain setup pulls prior sessions, your builder profile, recent design docs, and eureka moments so you're not starting cold. Use it before you write any code or run plan reviews. It's opinionated by design: the forcing questions are meant to make you uncomfortable if your idea is vague, which is the point.
npx skills add https://github.com/garrytan/gstack --skill office-hours