CLI violates instructions by ignoring mandatory Microsoft cpp language server (LSP) usage

### Describe the bug

Copilot CLI used grep/glob/raw search even though:

LSP was available
LSP would clearly have been sufficient

The model did not check for LSP availability
The model acknowledged the rule but still violated it.

[lsp_diagnostic_log_2026-05-25_16-06-45.zip](https://github.com/user-attachments/files/28224349/lsp_diagnostic_log_2026-05-25_16-06-45.zip)

Note 1: I'm using the cpp language server (https://github.com/microsoft/cpp-language-server).
Note 2: I've tried with many models (GPT-5 mini, Claude Sonnet 4.6, Claude Opus 4.6), but the output was always the same
### Affected version

GitHub Copilot CLI 1.0.54.

### Steps to reproduce the behavior

[lsp_diagnostic_log_2026-05-25_16-06-45.txt](https://github.com/user-attachments/files/28224382/lsp_diagnostic_log_2026-05-25_16-06-45.txt)

### Expected behavior

Follow instructions from \.github\instructions.md

### Additional context

_No response_

檢視 .github/instructions.md 和附加的診斷記錄，然後使用 Copilot CLI 1.0.54 和 Microsoft cpp language server 重現該行為。當 LSP 可用且足夠時，CLI 遵循所述的 LSP 使用指示，即視為完成；該 issue 未指定實作檔案或測試。

由索引模型根據 Issue 內容生成。