Wire-incompatible break with the 0.x protocol. Every host-side path (UART, USB CDC, framing, radio dispatcher, display update channel) speaks the v2 wire format defined in PROTOCOL.md.
* Replace the host framing path with streaming FrameDecoder + encode_frame from donglora-protocol, matching the new (type_id, tag, payload) shape.
* Update src/channel.rs and src/host/{uart,usb,framing}.rs for the new frame semantics: per-request tag echo, CRC checked in the decoder, async ERR fan-out on tag 0.
* Rework src/radio.rs to emit RX / TX_DONE / OK / ERR messages in v2 shape, including RxOrigin, TxDonePayload, and SetConfigResult codes.
* Update src/protocol.rs glue to re-export v2 types from donglora-protocol and drop the legacy 0.x shim surface.
* Refresh PROTOCOL.md to the v2 normative spec (kept in sync with the donglora-protocol crate).
* Minor display and main-loop cleanups needed for the new radio event shape.
swaits