fix(web): question count spans simultaneous question requests

Pi-style agents ask several one-question requests at once, so the per-prompt count never showed. derivePendingThreadRequests now groups user_input requests whose pending intervals overlap into one queue and flattens question positions across it: five concurrent asks read 1/5 through 5/5 and hold position as earlier ones resolve, while a question asked after the previous resolved starts a fresh queue. Mobile's collapsed bar uses the queue total too.
3c84e2f00bBen Davis committed on 10/24/2026, 5:16:23 AMparente92744d
5 files changedLine totals unavailable