Adds configuration for the new GPT-5 Pro model released by OpenAI.
Specifications from official docs:
- 400K context window
- 272K max output tokens (largest of GPT-5 family)
- Highest reasoning capability (5/5)
- Reasoning token support
- Vision input support (text+image input, text output only)
- No temperature support (fixed, like other reasoning models)
- Available via Responses API only (use_openai_response_api: true)
- Default reasoning effort: high
Accessible via alias 'gpt5pro'.