[Idea] 希望增加追加系统提示词以及覆盖系统提示词功能，还有就是查看默认系统提示词

[oneadms]

Before I submit

• I searched existing issues and didn't see a similar idea

My idea

需求背景： 看到一个文章通过追加系统提示词来防止GPT降智。 现在项目实现系统提示词应该是透传 只能通过下游来配置系统提示词

What problem does it solve? (optional)

No response

How important is it to me? (just a vibe check)

None