fix: harden cross-platform quality tooling

tools/fix_format.sh

@@ -6,14 +6,26 @@ set -euo pipefail
 ROOT="$(cd "$(dirname "$0")/.." && pwd)"
 cd "$ROOT"
 
+python_formatter() {
+  local python_command
+  for python_command in python python3; do
+    if command -v "$python_command" &>/dev/null &&
+      "$python_command" -m gdtoolkit.formatter --help &>/dev/null 2>&1; then
+      echo "$python_command"
+      return 0
+    fi
+  done
+  return 1
+}
+
 # detect gdformat
 FMT=()
 if [[ -x "$ROOT/.venv/bin/gdformat" ]]; then
   FMT=("$ROOT/.venv/bin/gdformat")
 elif command -v gdformat &>/dev/null; then
   FMT=(gdformat)
-elif python -m gdtoolkit.formatter --help &>/dev/null 2>&1; then
-  FMT=(python -m gdtoolkit.formatter)
+elif PYTHON_FORMATTER="$(python_formatter)"; then
+  FMT=("$PYTHON_FORMATTER" -m gdtoolkit.formatter)
 fi
 
 if [[ ${#FMT[@]} -eq 0 ]]; then