fix(distillation): 优化数据读取逻辑并返回字符串形式的翻译字段

- 修改变量名 `$user_group` 为 `$distillationWords` 以提高可读性
- 移除不存在数据时返回空数组的逻辑，改为抛出异常
- 将关联的 `trans` 数据转换为逗号分隔的字符串格式 `trans_str`
- 在返回结果中移除原始的 `trans` 字段
- 确保返回的数据结构一致性和清晰度

app/service/DistillationWordService.php

@@ -138,11 +138,14 @@ class DistillationWordService extends BaseService
      */
     public function readData(mixed $id): array
     {
-        $user_group = $this->dao->get(['id' => $id], ['*'], ['trans', 'expand']);
-        if (empty($user_group)) {
+        $distillationWords = $this->dao->get(['id' => $id], ['*'], ['trans']);
+        if (empty($distillationWords)) {
             throw new ApiException('数据不存在');
         }
-        return $user_group->toArray();
+        $data = $distillationWords->toArray();
+        $data['trans_str'] = implode(',', array_column($data['trans'], 'name'));
+        unset($data['trans']);
+        return $data;
     }
 
     /**