Document eligible OpenAI models for parse_via_chat_gpt flow webhook

[AmishaBisht]

Eligible models to publish

• gpt-5.1 — GPT-5 family
• gpt-5 — GPT-5 family
• gpt-5-mini — GPT-5 family
• gpt-5-nano — GPT-5 family
• gpt-4.1 — GPT-4.1 family
• gpt-4.1-mini — GPT-4.1 family
• gpt-4.1-nano — GPT-4.1 family
• gpt-4o — current webhook default
• gpt-4o-mini
• gpt-4-turbo — legacy
• gpt-3.5-turbo — legacy / cheapest
• o1, o3, o4-mini (reasoning) — caller must pass temperature: 1; webhook defaults to 0, which reasoning models reject