chat-duo (GTK client, DORMANT): logger-chat-duo.sqlite diagnostic logger

DORMANT since 2026-06-05 (Elazar's call - he uses chat-duo-web exclusively; no feature work, bug-only maintenance). GTK4 desktop client for llmmsg-srv, python package, repo /home/rob/agents/coder-chatduo. Ships its own append-only diagnostic logger (logger.py -> logger-chat-duo.sqlite, WAL, events table, disable via CHAT_DUO_LOG=0). No such sqlite exists on venus today - the client is not being run here, so it currently collects nothing. Registered so the fleet does not rediscover it as an unknown collector.