golang:1.25 and the stale almalinux9-gobuilder pin are replaced by
gobuilder:0.1.2-alma9 on every step that invokes the Go toolchain, with
GOCACHEPROG wired to the baked-in go-cache-plugin against the shared
S3 cache bucket.
- build.yaml/test.yaml/release.yaml: build+test steps use gobuilder,
cache env added
- pre-commit.yaml: switch pin, add cache (hooks run go vet/go test)
- lint step (test.yaml) and rpm/upload/release steps left untouched