cidx v3.0.0 — deleting the things that lied

cidx is a declarative CI/CD runner I build in Go. Its first major in a year ships five breaking changes, and every one of them removes a feature that looked like it worked: a 'build without push' mode that built nothing, a config key nothing read, a typo indistinguishable from a valid setting, tests covering less than advertised — and, found mid-sprint, a published Docker image that never contained the binary.