Remove the legacy HealthyPi 0x02 packet decoder

That single-sample combined format is no longer sent by current firmware,
which batches into the 0x03 (ECG/BioZ) and 0x04 (PPG) packets. Drops the
PacketSpec and decodeHealthypiPkt2; docs and code now agree.

flutter analyze clean (13 pre-existing infos); flutter test passes.

Author: awhitchurch

lib/boards/decoders/healthypi_decoders.dart

@@ -6,58 +6,11 @@ import 'dart:typed_data';
 import '../../protocol/decoded_packet.dart';
 import 'shared_codecs.dart';
 
-/// HealthyPi 5 (USB) — pktType 2 — Combined ECG, BioZ & PPG single-sample packet.
-///
-/// Payload layout (22 bytes):
-///   [0-3]    ecg_sample       int32  LE — sign-extended 24-bit ADC value
-///   [4-7]    bioz_sample      int32  LE — bio-impedance / respiration waveform
-///   [8]      bioZSkipSample   uint8  — 0 = valid BioZ; 1 = skip (do not plot/process)
-///   [9-12]   raw_red          int32  LE — PPG red-channel raw photodiode counts
-///   [13-16]  raw_ir           int32  LE — PPG IR-channel raw photodiode counts
-///   [17-18]  temp             int16  LE — °C × 100 (only low 16 bits of int32 used;
-///                                         e.g. 3650 → 36.50 °C)
-///   [19]     spo2             uint8  — SpO₂ in %
-///   [20]     hr               uint8  — heart rate in bpm
-///   [21]     rr               uint8  — respiration rate in breaths/min
-///
-/// Note: bioz_sample is always emitted in channelSamples. Consumers must check
-/// the 'bioZSkip' event flag (1 = invalid) before plotting or processing the
-/// 'bioz' channel for this sample.
-DecodedPacket decodeHealthypiPkt2(Uint8List p) {
-  final ecgSample = Codec.readInt32LE(p, 0).toDouble();
-  final biozSample = Codec.readInt32LE(p, 4).toDouble();
-  final bioZSkip = p[8] != 0; // true → firmware says skip this BioZ sample
-  final rawRed = Codec.readInt32LE(p, 9).toDouble();
-  final rawIr = Codec.readInt32LE(p, 13).toDouble();
-  final temp = Codec.readInt16LE(p, 17).toDouble() / 100.0;
-  final spo2 = p[19];
-  final hr = p[20];
-  final rr = p[21];
-
-  return DecodedPacket(
-    pktType: 2,
-    channelSamples: {
-      'ecg': [ecgSample],
-      'bioz': [biozSample], // check events['bioZSkip'] before using
-      'ppgRed': [rawRed],
-      'ppgIr': [rawIr],
-    },
-    events: {
-      'heartRate': hr,
-      'respRate': rr,
-      'spo2': spo2,
-      'temperature': temp,
-      'bioZSkip': bioZSkip ? 1 : 0,
-    },
-  );
-}
-
 // ── HealthyPi 5 firmware v1.0.0+ (USB) — separate ECG/BioZ and PPG packets ──
 //
-// From firmware 1.0.0, HealthyPi 5's USB stream batches samples into two
-// framed packet types instead of the combined single-sample packet above (see
-// README wire-format tables). All multi-byte fields are little-endian, matching
-// pktType 2 and the BLE stream (verified against ProtoCentral OpenView 2).
+// HealthyPi 5's USB stream batches samples into two framed packet types (see
+// the README wire-format diagram). All multi-byte fields are little-endian,
+// matching the BLE stream.
 
 /// HealthyPi 5 — pktType 3 — ECG + Respiration (BioZ) batch (USB).
 ///

lib/boards/descriptors/healthypi.dart

@@ -121,12 +121,6 @@ final BoardDescriptor healthypiDescriptor = BoardDescriptor(
     _ppgRedChannel,
   ],
   packets: [
-    PacketSpec(
-      pktType: 2,
-      label: 'ECG/BioZ/PPG-Red/PPG-IR/Temp/SpO2/HR/RR',
-      expectedPayloadLength: 22,
-      decode: decodeHealthypiPkt2,
-    ),
     // Firmware v1.0.0+ USB batch packets.
     PacketSpec(
       pktType: 3,