docs: update AI Gateway docs API reference and image generation (#5390)

* docs: update AI Gateway OpenAPI spec with latest types

Regenerate the OpenAPI spec to include recent schema changes:
- Add reasoning_options with budget_tokens parameter
- Add reasoning field to message content
- Add context_editing options (enabled, clear_tool_uses, clear_thinking)
- Update response types schema structure
- Various type refinements and fixes

Co-Authored-By: Connor Loi <loiconnor8@gmail.com>

* update openapi spec

* docs

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Co-authored-by: replicas-connector[bot] <replicas-connector[bot]@users.noreply.github.com>
Co-authored-by: Connor Loi <loiconnor8@gmail.com>

Author: replicas-connector[bot]