On both image routes, a request waits for an image another request is
making, and its client goes away. The first test wants that request
answered 499 and logged once at info level. It fails on next, which
answers 500 and logs it at error level. The second test pins the 500
that a cancellation keeps while the request's context is live; it
passes on next. The fix follows in the next commit.
Model: opus-5-5
