create_upload_url
Get a one-time URL to hand HERO a file you hold locally — in your code sandbox (e.g. a file the user uploaded to you, or a PDF/document you generated) or on disk — when it is too large to pass as base64 (anything over ~600KB). Requires that you can make an HTTP request yourself (a shell, code execution with network access, curl). Send the raw bytes with PUT to uploadUrl with the returned headers (the Authorization bearer token is the slot’s secret; X-Filename: <original name> keeps the name), then call import_file with the uploadId. Valid for 2 hours, one file, up to 50MB. If the request is blocked by your sandbox’s network policy, tell the user the HERO domain must be allowed for outbound requests, or ask for a direct-download link (import_file sourceUrl) instead.