Seed from go-template-repo, renamed to simplexcalc

The template's files at a77fd30, without its history or LICENSE, after
script/rename simplexcalc.

Model: opus-5-5

script/fmt-check

@@ -0,0 +1,25 @@
+#!/bin/sh
+# script/fmt-check: check formatting (read-only). Same scope as
+# script/fmt, but fails instead of writing.
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+
+    if [ -n "$(gofmt -s -l .)" ]; then
+        echo "gofmt needed on:"
+        gofmt -s -l .
+        exit 1
+    fi
+
+    # Exit 2 means no prettier and no docker: reported by
+    # script/prettier on stderr and not treated as a failure, so this
+    # check still runs on a machine that has neither. The container
+    # build is the gate that always has both.
+    "$SCRIPT_DIR/prettier" --check . || [ $? -eq 2 ]
+}
+
+main "$@"