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

script/precommit

@@ -0,0 +1,18 @@
+#!/bin/sh
+# script/precommit: run by the git pre-commit hook; fails the commit if
+# checks fail. Our own extension to scripts-to-rule-them-all.
+#
+# Runs lint and fmt-check but deliberately NOT the tests, so the TDD
+# red-phase commit (failing tests, no implementation yet) can land. CI
+# runs make check via docker build, which catches any branch that
+# ships red.
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+
+main() {
+    "$SCRIPT_DIR/lint"
+    "$SCRIPT_DIR/fmt-check"
+}
+
+main "$@"