release: 3.18.0 (#3936)

Automated Release PR
---


##
[3.18.0](https://github.com/openai/openai-python/compare/v3.17.0...v3.18.0)
(2026-09-22)


### Features

* **api:** add GPT-6 Sol and Luna model identifiers
([#3935](https://github.com/openai/openai-python/issues/3935))
([455ce1b](https://github.com/openai/openai-python/commit/455ce1b5da067e5d7631c86a571ca3b0d03b65cd))

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