WireCodec

Pure codec for wire framing and protobuf serialization.

Handles framing per protocol.md §2 (TCP/Serial stream framing with resync) and encodes/decodes protobuf envelopes. No I/O, no state machines — just encode/decode.

Framing format (TCP & Serial transports):

+------+------+----------+----------+==================+
| 0x94 | 0xC3 |   LEN_HI |   LEN_LO |  protobuf bytes  |
+------+------+----------+----------+==================+

• Sync bytes: 0x94 0xC3

• Length: big-endian uint16 (payload only, excludes 4-byte header)

• Max payload: 512 bytes