Leave Web Room

Public: release a seat when a visitor closes their tab.

Best-effort — a browser that dies without sending this leaves the seat held, which is what the stale-session sweep is for. Returning 200 for an unknown room keeps this safe to call blindly from beforeunload.

failed=true means the browser never reached the room (the SDK would not load, or room.connect timed out). That attempt is refunded: it would otherwise burn one of three daily demos without the visitor hearing anything. See _refund_public_demo.