Visualises the chat read-receipt metrics added with the read-receipt feature
(the dashboard was deferred there per the owner): posted rate by kind, the
unread backlog (chat_unread_messages gauge), and the publish-to-read latency
(chat_read_duration — average by kind plus overall p50/p95). Mirrors the
game-domain dashboard's structure; the file provider auto-discovers it.
Ilia Denisov