Re-vendor the canonical files from sneak/prompts at dd4027b (closes #13)

`.dockerignore`, `.gitignore`, `.golangci.yml` and the workflow are their
copies at that commit. This repo's own entries are kept after the
canonical content: the anchored `/attrsum` binary, the Go entries in
`.gitignore`, and tabs for `*.go` in the new `.editorconfig`.
`REPO_POLICIES.md` is new. The workflow keeps `fetch-depth: 0`, which the
policies require of a repo that stamps a tag-derived version.

The lint phase moves to golangci-lint v2.14.0, which finds nothing in
the code. `script/fmt` now runs goimports with `go run` at its pinned
commit. A version-checked install by `script/bootstrap` would have to be
found on `PATH`, and the CI runner's `PATH` lacks Go's bin directory.

Model: opus-5-5

TODO.md

@@ -28,9 +28,9 @@ Author are missing)
     `dd4027b`: `REPO_POLICIES.md` and `.editorconfig` added;
     `.dockerignore`, `.gitignore`, `.golangci.yml` and the workflow
     refreshed, keeping this repo's own entries and `fetch-depth: 0`;
-    the lint phase runs golangci-lint v2.14.0; `script/bootstrap`
-    installs goimports unless the installed one has the pinned version,
-    and it and `script/fmt` put Go's bin directory on `PATH`
+    the lint phase runs golangci-lint v2.14.0; `script/fmt` runs
+    goimports with `go run` at its pinned commit instead of
+    `script/bootstrap` installing it
 * 2026-10-06: the summary line after `sum`, `check` and `clear` prints
     the byte unit once (`1.5 KiB`, not `1.5 KiB bytes`)
 * 2026-10-06: a path that `--exclude` or `--exclude-dotfiles` excludes

script/bootstrap

@@ -3,19 +3,13 @@
 # this repo. Idempotent: every install is guarded by a check so already
 # installed tools are skipped. Base tooling comes from nix, apt, brew,
 # or apk (detected in that order); assumes nothing is present.
-# goimports is installed via `go install` at a pinned commit (never
-# "latest"), unless the installed one already has the pinned version.
-# The linter is not installed: it runs only as the lint phase of the
-# Dockerfile.
+# goimports is not installed: script/fmt runs it with `go run` at a
+# pinned commit. The linter is not installed: it runs only as the lint
+# phase of the Dockerfile.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
-# Pinned versions, 2026-10-05
-# GOIMPORTS_REF is the commit tagged GOIMPORTS_VERSION.
-GOIMPORTS_VERSION="v0.42.0"
-GOIMPORTS_REF="golang.org/x/tools/cmd/goimports@009367f5c17a8d4c45a961a3a509277190a9a6f0"
-
 PKGMGR=""
 SUDO=""
 APT_UPDATED=""
@@ -63,30 +57,6 @@ missing() {
     ! command -v "$1" >/dev/null 2>&1
 }
 
-# Print the version the goimports on PATH was built from, or nothing.
-# goimports has no version flag; `go version -m` reads the binary's
-# build info, whose "mod" line names the module and its version.
-goimports_version() {
-    if missing goimports; then return 0; fi
-    go version -m "$(command -v goimports)" 2>/dev/null |
-        awk '$1 == "mod" { print $3 }'
-}
-
-ensure_goimports() {
-    if [ "$(goimports_version)" = "$GOIMPORTS_VERSION" ]; then
-        echo "goimports $GOIMPORTS_VERSION already installed"
-        return 0
-    fi
-    go install "$GOIMPORTS_REF"
-    hash -r
-    if [ "$(goimports_version)" != "$GOIMPORTS_VERSION" ]; then
-        echo "bootstrap: goimports on PATH is not $GOIMPORTS_VERSION:" \
-            "$(command -v goimports)" >&2
-        exit 1
-    fi
-    echo "goimports $GOIMPORTS_VERSION installed"
-}
-
 main() {
     cd "$ROOT"
 
@@ -94,12 +64,6 @@ main() {
     if missing make; then pkg_install gnumake make make make; fi
     if missing go; then pkg_install go golang go go; fi
 
-    # go install writes to Go's bin directory, which need not be on PATH.
-    gobin="$(go env GOBIN)"
-    [ -n "$gobin" ] || gobin="$(go env GOPATH)/bin"
-    PATH="$gobin:$PATH"
-    ensure_goimports
-
     go mod download
 
     echo "bootstrap complete"

script/fmt

@@ -4,15 +4,14 @@ set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
+# goimports v0.42.0, 2026-10-05. Run with `go run` at this commit rather
+# than installed, so it is always this version, whatever is on PATH.
+GOIMPORTS_REF="golang.org/x/tools/cmd/goimports@009367f5c17a8d4c45a961a3a509277190a9a6f0"
+
 main() {
     cd "$ROOT"
-    # script/bootstrap installs goimports into Go's bin directory, which
-    # need not be on PATH.
-    gobin="$(go env GOBIN)"
-    [ -n "$gobin" ] || gobin="$(go env GOPATH)/bin"
-    PATH="$gobin:$PATH"
     gofmt -s -w .
-    goimports -w .
+    go run "$GOIMPORTS_REF" -w .
 }
 
 main "$@"