console.* calls and uncaught errors from the page — warnings and errors unless debug.

Capped at the most recent MAX_BROWSER_LOGS; browserLogsDropped counts what was dropped. The cap is not tidiness: unlike tests and notices, page output is bounded by nothing — one for loop around console.warn produced 50,001 entries and 252 MB of retained heap. The newest are kept because they are the ones adjacent to the failure being diagnosed.