main.go always sets both Channels and Registry together, making the
Channels fallback paths dead code. This removes:
- Server.Channels field from the Server struct
- 3 if/else fallback blocks in handlers_session.go (replaced with
Registry.FindChannelForStage, SearchSessions, SearchStages)
- 1 if/else fallback block in handlers_guild_ops.go (replaced with
Registry.NotifyMailToCharID)
- 3 method fallbacks in sys_channel_server.go (WorldcastMHF,
FindSessionByCharID, DisconnectUser now delegate directly)
Updates anti-patterns.md #6 to "accepted design" — Session struct is
appropriate for this game server's handler pattern, and cross-channel
coupling is now fully routed through the ChannelRegistry interface.
The config package used `package _config` with a leading underscore,
which is unconventional in Go. Rename to `package config` (matching the
directory name) and use `cfg` as the standard import alias across all
93 importing files.
