Custom instructions leak into repository analysis

### Describe the bug

Whenever I ask copilot to analyze a repository and e.g. create an instruction file it seems that it is leaking local instructions into the context and taking them for facts for this particular repository.

This then can lead of general part in the instructions, e.g. I have

```
### Markdown

- Start each sentence on a new line to improve diff readability.
- Format tables with aligned spaces so they are readable as plain text.
```

that now suddenly is in-cooperated whenever I use e.g. `/init` or asking for an `AGENTS.md` file or enhance/create an inital readme for the project.

### Affected version

_No response_

### Steps to reproduce the behavior

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

首先使用 /init 或 AGENTS.md 生成请求复现该行为，并将生成的仓库指令与报告中描述的本地自定义指令进行比较。当通用的本地 Markdown 指导不再被纳入为仓库特定事实时，即表示完成。

由索引模型根据 Issue 内容生成。