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 產生請求重現該行為，並將產生的儲存庫指示與報告中描述的本機自訂指示進行比較。當通用的本機 Markdown 指導不再被納入為儲存庫特定事實時，即表示完成。

由索引模型根據 Issue 內容生成。