Background windows stopped updating because the reaper suspended contexts
after ContextSuspendAfter and fully reaped them after ContextTTL. Suspended
contexts had to re-run the page init function from scratch on reconnect,
losing the live-updating experience.
Contexts now live until the browser tab closes (beforeunload beacon) or
the server shuts down. The context map grows indefinitely — no background
reaper.
Removes: startReaper, reapOrphanedContexts, suspend/resume logic,
ContextSuspendAfter/ContextTTL config fields, lastSeenAt/suspended
context fields, and all associated tests.
