When --onedrive-av-override is set and the object is malware-flagged,
download via Microsoft Graph beta contentStream then /content with
Prefer: forceInfectedDownload, and keep Prefer (and AVOverride) on the
SharePoint redirect without re-encoding tempauth.
Clean files keep using the stable v1.0 /content path so permanently
enabled av_override does not put all traffic on beta APIs.
AI-assisted change; tested against OneDrive for Business with
application permissions (client_credentials).
The unauthenticated follow-up to /content redirects used Client.Do,
which does not check HTTP status. A 403 malwareDetected JSON body was
therefore written as file content and surfaced only as a size mismatch.
Check the status code, surface malware errors clearly, and avoid
suggesting --onedrive-av-override when it is already set.