Introduces the voltex_net crate (no external dependencies) with a binary
Packet protocol over UDP. Supports 6 variants (Connect, Accept, Disconnect,
Ping, Pong, UserData) with a 4-byte header (type_id u8, payload_len u16 LE,
reserved u8) and per-variant payload encoding. Includes 7 unit tests covering
all roundtrips and invalid-type error handling.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
