gofumpt was pinned only by its version tag. It is now a tool of a
separate module in tools/, so `go tool` builds it from source checked
against the hashes in tools/go.sum, and mfer's own module gains no
dependencies. script/prettier no longer falls back to a prettier on
PATH, and fails when node_modules holds a different version than
package.json pins. The bootstrap comment now says what --frozen-lockfile
really does, package.json drops its made-up version, and the golang
image comment names its exact version.
Model: opus-5-5
Adds .prettierrc and .prettierignore, a single script/prettier entrypoint shared by fmt and fmt-check so the two cannot drift, and prettier 3.9.6 pinned by yarn.lock integrity hash.
Markdown formatting is now gated in the authoritative Docker build via a new mdfmt stage, since the golangci-lint image has no node. REPO_POLICIES.md is ignored so local tooling cannot drift it from upstream.
Removes the || true that made the previous prettier invocation unable to fail.
clawbot