script/bootstrap credited the goimports pin to script/fmt-check, which
runs gofmt only; the header now credits script/fmt. script/cibuild
still described the Dockerfile as running make check, which stopped
being true once linting moved to its own stage. The docker-missing
warning in script/bootstrap is one sentence instead of three fragments
each carrying the bootstrap: prefix. Dockerfile.lint now states the
residual risk of skipping golangci-lint config verify: unknown
top-level keys in .golangci.yml are ignored silently, so a mistyped key
lints clean and applies nothing.
Comment and message text only; no behaviour changes.
