WebFetch now returns structured HTTP failure information when a server responds with an error status, including status text and Retry-After when present. This should help users distinguish an authentication-required page, a rate limit, and a normal fetch failure without guessing from a generic exception.
Evidence
WebFetch HTTP error result text (search for "The server returned HTTP" and "The response body was not retrieved")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.