ctxerrors v0.7.0 — remove HTTP-specific ErrUnexpectedHTTPStatusCode commerr holds transport-agnostic sentinels; an HTTP-status error is not one, so ErrUnexpectedHTTPStatusCode is removed (61 -> 60). Define HTTP-status sentinels in an HTTP package instead (aichteeteapee has ErrUnexpectedResponseStatus). Rate-limit and auth sentinels stay -- they are not HTTP-only. Breaking.