script/loadtest, added in the next commit, needs an upstream host that
answers any path with the same image, so each new path is a new source
image for pixad to fetch. This test checks that the origin's handler
answers several paths with 200, Content-Type image/jpeg and the same
bytes, and that the image decodes as a JPEG of the expected size. It
does not build until the origin exists.
Model: opus-5-5
