Download a public Drive file by share-URL.
Handles the virus-scan interstitial path automatically and applies magic-bytes MIME sniffing when Drive returns a generic content-type.
Any Drive share URL (see extractFileId).
Bytes + MIME + size + filename ready to forward to Gemini.
On invalid URL (400), file too large (413), or upstream failure / non-public file (502).
Download a public Drive file by share-URL.
Handles the virus-scan interstitial path automatically and applies magic-bytes MIME sniffing when Drive returns a generic content-type.