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

@@ -0,0 +1,26 @@
+#!/bin/sh
+# script/fmt: format all files (writes). Go via gofmt, everything else
+# (markdown, CSS, JS, YAML, JSON) via prettier with the repo's
+# .prettierrc. Never hand-rolled substitutions: this script is the only
+# sanctioned way to reformat the tree.
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+
+    gofmt -s -w .
+
+    if command -v goimports >/dev/null 2>&1; then
+        goimports -w .
+    fi
+
+    # A missing runner (exit 2) is a warning here: script/prettier has
+    # already said so on stderr, and failing `make fmt` over it would
+    # block work that has nothing to do with markdown.
+    "$SCRIPT_DIR/prettier" --write . || [ $? -eq 2 ]
+}
+
+main "$@"