2-state read receipts (sent / read) via two custom packets:
MarkConsoleRead (client->server, header 4085) sent on thread focus,
relayed by the emulator to the peer as ConsoleReadReceipt (server->
client, header 4086). Client marks own messages READ and renders
checkmarks. Live-relay only (no DB table / login batch) since the
client doesn't persist message history across sessions.
simoleo89