Serves one static HTML page, accepts WS connections, broadcasts
room_state/log/metric messages to all clients. Replays current
state to late-joining clients so refreshing the dashboard during
a run shows the right grid. Exposes a reporter() method that
returns a DashboardReporter scenarios can call without knowing
about sockets.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
