可不可以切换某个供应商时设置单独的提示词

### Self Checks / 自检

- [x] I have read the [FAQ](https://github.com/farion1231/cc-switch#faq) section in README.
我已阅读 README 中的[常见问题](https://github.com/farion1231/cc-switch#常见问题)。

- [x] I have searched for [existing issues](https://github.com/farion1231/cc-switch/issues), including closed ones.
我已搜索过[已有的 Issue](https://github.com/farion1231/cc-switch/issues)，包括已关闭的。

### Related App / 涉及应用

Claude Code, General / 通用

### Problem or Motivation / 问题或动机

目前配置了很多供应商，针对不同的供应商其实想设置不同的提示词，比如如果想把其他非官方模型接入Claude code的话，需要用特殊的提示词进行配置，这个时候就得单独去提示词界面去切换。

### Proposed Solution / 建议方案

如果能直接在编辑供应商的时候单独加一栏使用单独提示词就好了

### Additional Context / 补充信息

_No response_

### Contribution / 参与贡献

- [x] I am interested in contributing to this feature.
我有兴趣参与开发此功能。

The issue names no files or tests; start by tracing the provider-editing entry point and the existing prompt-switching screen. Confirm how provider settings are stored, then verify that editing a provider can select an independent prompt and that switching providers applies it.

Written by the indexing model from the issue text.