CI duplicated the Makefile's steps and built the binary without -trimpath
or the version-stamped -ldflags, so it could pass while make build failed
and the CI binary reported dev. Make the Makefile the single build
definition: CI now runs make test and make build, then prints the binary's
build info as evidence of the version stamp.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>