A route that aborts its storage read when the response closes rejects with
AbortError after the client has gone. The error handler reported that
cancellation as a server crash. Skip the error sinks for an AbortError when
the response was closed before it finished; report it otherwise.
Fixes PAPERCLIP-BACKEND-5A
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>