v0.4.0-next.7

The realtime rebuild: one shared RealtimeSession under the doorbell and every room (each connection scar written once), bool.room becomes callable for named rooms — bool.room("game:4") — with the identical surface, and behavior otherwise unchanged (all pre-rewrite tests pass verbatim). Verified against real infra: default-room state flow, scoped-room isolation under policy v4, and hard-drop recovery.