script/test ended with a verbose rerun whose exit status became the
script's, so a test that failed once and passed on the retry gave a
green build. It now follows the REPO_POLICIES.md pattern: go vet, then
go test -count=1 -timeout 30s -race -cover; on failure a verbose rerun
for the details, then exit 1. -count=1 stays on both go test lines
because the Dockerfile keeps Go's build cache between builds.
Model: opus-5-5
make test and make build in the Dockerfile now share one Go build cache,
kept in a BuildKit cache mount with this repository's own id, so they
compile only what changed. script/test passes -count=1.
Model: opus-5-5