Both Go peer and browser now broadcast {type:"presence", from, role}
every 10s on the bus. When either side sees a presence from someone
they don't yet have a RTCPeerConnection to, they initiate a new one
targeted at that specific peerID via the new "to" field on signal
messages. Each side keeps a map<peerID, RTCPeerConnection> instead of
the v0.3 single-connection model.
This means:
- N browsers can pair with M peers (true mesh)
- New tabs auto-discover existing peers via their next 10s chirp
- Restarts and network blips recover within 10s instead of needing
a manual browser refresh
- 45s lastSeen timeout sweeps disconnected peers and tears down their
PeerConnection
The browser UI now shows a row of peer chips that flip green when their
DataChannel opens. The pill shows "rtc" if *any* peer is open, else
"negotiating" if any are in progress, else "sse".
Go side regenerates a random peerID per process start (was static).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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