Copilot suddenly refusing to assist with valid requests

### Describe the bug

Copilot CLI for the past few versions has suddenly started to refuse valid and safe requests. Even with a clean context and just AGENTs.md file and skills loaded.

Prompts mentioning tests, fixing bugs, asking for what's in the repo's directories, or otherwise have mostly come back with "I'm sorry, but I cannot assist with that request".

I'm using GPT 5 Mini on Medium reasoning.

### Affected version

1.0.47

### Steps to reproduce the behavior

1. Open Copilot CLI in a directory of a local repo
2. Ask Copilot to fix a bug, issue, or answer a question about a repository that Copilot has access to
3. Copilot refuses with "I'm sorry, but I cannot assist with that request"

### Expected behavior

1. Open Copilot CLI in a directory of a local repo
2. Ask Copilot to fix a bug, issue, or answer a question about a repository that Copilot has access to
3. Copilot responds to the request

### Additional context

Operating System: Windows
CPU Architecture: x86_64
Terminal Emulator: Windows Terminal
Shell: Powershell 7 (7.6.1)

Start by reproducing the refusal in Copilot CLI 1.0.47 on Windows with PowerShell 7.6.1, using GPT 5 Mini on Medium reasoning and the repository context described. Try the listed prompts, then compare the result with the expected behavior: valid repository questions and coding requests should receive a response rather than the refusal message.

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