Breakout rooms: moderator overview to see and drop in on rooms without leaving the main room

Is your feature request related to a problem? Please describe.

When students are in breakout rooms, a teacher cannot see what is happening in them without joining each room in turn. Joining a room opens a separate session, and moving between rooms costs instructional time. With young students (feedback from an elementary online school), teachers need to notice quickly which group needs help and step in, much as they would walk around a physical classroom.

Describe the solution you'd like

A breakout monitoring view for moderators in the main room, for example a ribbon or grid with one tile per room (similar to the webcam ribbon, but per room rather than per participant). Selecting a room tile would let the moderator:

• see who is in the room and preview it — participant webcams and/or the room's whiteboard/presentation (low-resolution or thumbnail is enough);
• listen to the room;
• speak into the room;

without leaving the main room or opening the breakout room's own session.

Describe alternatives you've considered

What exists today on 4.0.0-rc.3:

• Listen to room in the running breakout panel moves the moderator's audio into the room with microphone publishing allowed, so they can hear and speak while staying in the main room. This covers the audio part, but it is not discoverable as a monitoring tool and there is no visual.
• The breakout panel lists who is in each room.
• Join room opens the room in a new window, which gives full visibility but takes the teacher out of the main room.

Additional context

The listen-in mechanism (breakout-listen LiveKit membership) could be the audio basis for the tile. Visual preview would need a lightweight subscription to a room's webcams or a periodic whiteboard/presentation snapshot per room.