Adopt scripts-to-rule-them-all: script/ entrypoints, Makefile shims

script/lint

@@ -0,0 +1,23 @@
+#!/bin/sh
+# script/lint: run the linter. CGO dependencies (pkg-config, vips,
+# libheif) come from nix-shell when not already available (e.g. inside
+# a Docker build or an existing nix-shell).
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+run_with_cgo_deps() {
+    if command -v pkg-config >/dev/null 2>&1; then
+        sh -c "$1"
+    else
+        nix-shell -p pkg-config vips libheif golangci-lint git --run "$1"
+    fi
+}
+
+main() {
+    cd "$ROOT"
+    echo "Running linter..."
+    run_with_cgo_deps "golangci-lint run"
+}
+
+main "$@"