The header's clocks start last in init, after the rounds, and an error
formatting them, as in a browser that rejects the "shortGeneric" time
zone name, leaves both clocks blank instead of stopping the page before
its first round. updateClocks moved out of init so a unit test can call
it.
The footer legend's red entry reads >=500ms, as README.md and
CONFIG.latencyColors have it. buildUI is exported so a unit test can draw
the page and check the legend against every entry of
CONFIG.latencyColors.
Model: opus-5-5
