chore: return raw in response generated by generate

[nsrCodes]

• to make it possible to extract segments and words from verbose responses in transcription flows as describe in [JS] Pipeline for transcription using the whisper model seems broken #3366

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[MichaelDoyle]

Hey @nsrCodes - typically "custom" should contain the raw response. It's possible the oai plugin needs to be adjusted to set custom as the raw response here.

I think we do want to move to using raw for this purpose (its clearer that way), but we are in a bit of a between state right now.