docs: add GPTZZZ provider

[pbhhdf]

GPTZZZ is an OpenAI-compatible gateway. This adds a section to the providers page in the same shape as the other custom-config entries.

Placed between Google Vertex AI and Groq to keep the alphabetical ordering.

What the section covers

The config block, with @ai-sdk/openai-compatible and baseURL set to https://gptzzz.ai/v1.

A note that the catalog differs between account groups, with the curl to list the real IDs, so nobody copies the two example model IDs and finds their account does not serve them.

A tip about reasoning_effort, because the accepted values are not uniform across the catalog. Verified against the live endpoint on 2026-09-16: gpt-6-astra accepts low, medium, high, xhigh and max and rejects none, while gpt-5.6, gpt-5.6-sol and gpt-5.6-terra also accept none.

{"model":"gpt-6-astra", ..., "reasoning_effort":"none"}
{"error":{"message":"Unsupported value: 'none' is not supported with the 'gpt-6-astra' model. Supported values are: 'low', 'medium', 'high', 'xhigh', and 'max'.","type":"invalid_request_error"}}

Note on /connect

The section documents the config-block path, which works today. A Models.dev entry is open at anomalyco/models.dev#7214; once that merges, /connect will also list GPTZZZ and the explicit models map becomes optional. Happy to follow up with a short edit then, or to hold this until that lands if you would rather the two go in together.

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