handleSelect function

function handleSelect(step: FlowStep): StepResult {
  const el = requireElement(step);
  ensureVisible(el);

  if (!(el instanceof HTMLSelectElement)) {
    return { status: "failed", error: "Select target is not a <select>" };
  }

  if (step.selectIndex != null) {
    if (step.selectIndex >= 0 && step.selectIndex < el.options.length) {
      el.selectedIndex = step.selectIndex;
    } else {
      return {
        status: "failed",
        error: `Select index ${step.selectIndex} out of range`,
      };
    }
  } else if (step.selectText != null) {
    const option = Array.from(el.options).find(
      (o) => o.text === step.selectText || o.value === step.selectText,
    );
    if (option) {
      el.value = option.value;
    } else {
      return {
        status: "failed",
        error: `Option "${step.selectText}" not found`,
      };
    }
  }

  el.dispatchEvent(new Event("change", { bubbles: true }));
  return { status: "success" };
}