Uploading images to GitHub PRs from the CLI

GitHub has no public API for uploading images to PR descriptions. The drag-and-drop in the web UI uses an undocumented endpoint (/upload/policies/assets) that requires browser session cookies – you simply can not call it with an API token or gh.

The GitHub CLI team explicitly closed this as “not planned”, with the explanation that the upload flow requires a browser to obtain temporary S3 credentials. Pretty understandable but still tough to live with, particularly in this agent era we live in.