The go-nostr RelayConnect returns immediately after the WebSocket
handshake, but the relay has not yet sent the AUTH challenge. Calling
relay.Auth() right away signs the auth event with an empty challenge
tag, which the Buzz relay rejects permanently ('verification failed'
then 'authentication already failed' on retries).
Add a 2s sleep between RelayConnect and Auth() to give the background
read loop time to receive and store the challenge. The relay typically
delivers it within a few hundred milliseconds.
Implements a Buzz channel backed by a Nostr relay:
- kind:9 events scoped by "h" tag, "p" tags for mentions
- NIP-42 (kind:22242) auth before subscription
- optional threaded replies via "e" tag
- registered as config.ChannelBuzz with BuzzSettings
