getMode method
Gets the build mode as a command-line flag.
Returns:
- '--debug'if debug flag is set
- '--profile'if profile flag is set
- '--release'as default if neither debug nor profile is set
Example:
final modeFlag = argResults.getMode();
// Returns '--debug', '--profile', or '--release'
Implementation
String getMode() {
  String mode = '--release';
  if (getFlagDebug()) {
    mode = '--debug';
  } else if (getFlagProfile()) {
    mode = '--profile';
  }
  return mode;
}