func deferDeleteTempFile(path string) {
	tempFilesMu.Lock()
	tempFiles = append(tempFiles, path)
	tempFilesMu.Unlock()
}

// cleanupTempFiles removes any temporary files selected for deferred cleaning.
func cleanupTempFiles() error {
	tempFilesMu.Lock()
	defer tempFilesMu.Unlock()
	var lastErr error
	for _, f := range tempFiles {
		if err := os.Remove(f); err != nil {
			lastErr = err
		}