GitHub Copilot CLI error with Codex 5.3

### Describe the bug

I'm getting server error when using Codex 5.3, tested with GitHub Copilot CLI v0.0.420. Other models do work.

### Affected version

GitHub Copilot CLI 0.0.420.

### Steps to reproduce the behavior

1. Start GitHub Copilot CLI
2. Select model Codex 5.3
3. Enter a prompt (any prompt)

### Expected behavior

The LLM/AI should write a response. Instead of it, I get "server error".

### Additional context

Linux x86