Creates a completed session from audio that Blueprint downloads from the supplied fileUrl, then generates documentation asynchronously. This is the API-only path — there is no endpoint that accepts audio bytes. A 201 means the request was accepted, not that the audio was fetched or processed; listen for the progress_note_generated or session_transcript_error webhook. The clinician is taken from the client's primary clinician and cannot be chosen here, and usingHeadphones is accepted but not applied on this endpoint.