Build the canonical audio ModelMessage from an AudioChunk.
The content is [textPart?, fileAudioPart]: a raw-PCM16 AI-SDK file
part (mediaType: "audio/pcm16"), preceded by a transcript text part when
the chunk carries one. Audio travels cleanly in any role — no
forceUserRole.
Build the canonical audio ModelMessage from an AudioChunk.
The content is
[textPart?, fileAudioPart]: a raw-PCM16 AI-SDKfilepart (mediaType: "audio/pcm16"), preceded by a transcript text part when the chunk carries one. Audio travels cleanly in any role — noforceUserRole.