Static HTML page served by DashboardServer. Renders the 2×2 room
grid with progress bars and player tiles, subscribes to WS events,
updates tiles live. Click-to-watch modal is wired but receives
frames once the CDP screencaster ships in Task 22.
Adds escapeHtml() on all user-controlled strings (roomId, player
key) — not strictly needed for our trusted bot traffic but cheap
XSS hardening against future scenarios that accept user input.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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