Server.Start ran the loop that works out the home page's cards on the
context it was given. fx ends that context once start-up is done, so the
cards were worked out once and never again. The loop now runs on a
context that only Stop ends, as the other background parts do. Stop
waits for the loop to return, until its own context ends, before it
stops the HTTP server.
A new test starts a server in a synctest bubble and ends its context at
once. On the bubble's fake clock, the cards must be worked out again a
minute later, and not after Stop.
Model: opus-5-5
sneak