[09] Port the TCP105 board wire protocol

[jvwaldrich0]

Task 09 of 16 — these are sequential, do them in order.

Previous: #11 · Next: #13

Port target: cloudpark-toolkit (Go) → this repo (Rust). Reference paths below are relative to that repo.

Goal

Port the TCP105 totem-board wire protocol (framing + opcodes + IO word). Task 12 builds the server on top.

Scope

• STX = 0x7F framing, encode/decode with length + checksum exactly as the Go package.
• Opcodes: ResetBoard 0x01, VersionInfo 0x02, UpdateConfig 0x03, CPUUniqueCode 0x09, RFIDReader 0x11, SerialTransfer 0x19, GetIOStatus 0x42, UploadIOStatus 0x43, RelayControl 0x46, VoiceBroadcast 0x51.
• Serial ids: Serial1 = 0x01, Serial2 = 0x02 (printer path).
• 32-bit IO-status word with the exact bit positions: Input1 = 22, Input2 = 21, Input3 = 19 (loop detector), Input4 = 18 (pick-card button), Input5 = 17 (help button).
• Helpers to parse relay-control and config payloads.

Reference

cloudpark-toolkit/internal/tcp105proto/protocol.go (192 lines) + protocol_test.go

Done when

• Encode/decode round-trip tests for every opcode.
• IO-word bit set/clear tests assert the exact bit indices above.
• A frame with a bad STX or checksum errors instead of panicking.