These tests fail until the change that follows: runApp and
WaitForProcessing do not exist yet, the server has no shutdowner, and a
Sentry DSN that cannot be used exits the process from a goroutine
instead of failing the server's start hook.
runApp must return the exit code a shutdown request carries, 0 without
one, and 1 when the app fails to start or stop. A listen error must ask
fx to shut down with exit code 1. WaitForProcessing must wait for an
image being processed and report it when its context ends first.
Model: opus-5-5
