Adds real diagnostics: connection-level errors are now recorded and shown in the panel, rate limited so they can never slow it down. Previously these happened in a detached part of the worker and were invisible, which made problems hard to trace. Also stops normal client behaviour being treated as an error: a client asking for UDP on a non-DNS port (constant, for QUIC) and a blocked host now close cleanly instead of running the error path. Includes all 4.6.x fixes for the main causes of 1101.