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)

Inizia riproducendo il rifiuto in Copilot CLI 1.0.47 su Windows con PowerShell 7.6.1, usando GPT 5 Mini con Medium reasoning e il contesto del repository descritto. Prova i prompt elencati, quindi confronta il risultato con il comportamento previsto: le domande valide sul repository e le richieste di programmazione dovrebbero ricevere una risposta invece del messaggio di rifiuto.

Scritto dal modello di indicizzazione a partire dal testo della issue.