serde_yaml is deprecated and unmaintained. serde_yaml_ng is the community
fork with a compatible API, so this is a straightforward rename across the
codebase.
The API reference for `response_format` says:
> This parameter isn't supported for gpt-image-1 which will always return base64-encoded images.
Related to https://github.com/etkecc/baibot/issues/40
