TCP/TLS connection over SOCKS5 proxy to Mumble servers for text chat.
Minimal varint/field protobuf encoder/decoder (no external dep) handles
Version, Authenticate, Ping, ServerSync, ChannelState, UserState, and
TextMessage message types. MumbleBot exposes the same duck-typed plugin
API as Bot/TeamsBot/TelegramBot. 93 new tests (1470 total).
