插件参数设置默认值会自动加转义双引号

**Describe the bug**
工作流大模型节点在技能中使用插件，插件参数设置默认值会自动加转义双引号

**Screenshots**

**Version:**
最新代码本地make server启动

No source file or test is named. Reproduce the issue in the workflow large-model node by using a plugin inside a skill and setting a default parameter value, then trace where that value is serialized. Done means the default value no longer gains escaped double quotes; add or update a focused regression test if the relevant test location becomes clear.

Written by the indexing model from the issue text.