fix: bound live realtimeRr, stop fabricating activity/steps for the historical record family

lib/src/live.dart

@@ -183,7 +183,10 @@ RealtimeRrResult? realtimeRr(String hex) {
   final first = cntOff + 1;
   for (int i = 0; i < n && first + 2 * i + 2 <= b.length; i++) {
     final v = view.getInt16(first + 2 * i, Endian.little);
-    if (v > 0) rrMs.add(v);
+    // Same physiological range records.dart and control.dart gate on — a
+    // misaligned or corrupted slot should not reach live HRV/breathing
+    // compute as a beat just because this decoder forgot to check it too.
+    if (v >= kMinRrMs && v <= kMaxRrMs) rrMs.add(v);
   }
   return rrMs.isNotEmpty ? RealtimeRrResult(ts, rrMs) : null;
 }
@@ -334,8 +337,13 @@ DecodedSample? decodeRecord(String hex) {
     return DecodedSample(
       ts: d.tsEpoch,
       hr: d.hr,
-      activity: 0,
-      stepsInc: 0,
+      // This record family carries no IMU stepping window at all — that is
+      // "no usable IMU data", the same absence [DecodedSample.activity]'s
+      // doc comment describes for a truncated R10, not a measured 0.0/0.
+      // Fabricating zero here is the exact bug this decoder family was just
+      // fixed to stop making for R10.
+      activity: null,
+      stepsInc: null,
       wristOn: d.hr > 0,
       recType: recType,
     );

test/decode_guards_test.dart

@@ -204,6 +204,19 @@ void main() {
       // decodeRecord never invents a timestamp for a layout we cannot read.
       expect(decodeRecord(_patched(_goodV24, {1: 11})), isNull);
     });
+
+    test('the routed historical family reports null activity/steps, not 0/0',
+        () {
+      // v7/v9/v12/v18/v24 carry no IMU stepping window at all — that is the
+      // same "no usable IMU data" absence as a truncated R10, not a measured
+      // zero-motion reading. Fabricating 0 here silently misreports "this
+      // record type cannot say" as "the wrist was still".
+      for (final version in [9, 12, 18, 24]) {
+        final s = decodeRecord(_patched(_goodV24, {1: version}))!;
+        expect(s.activity, isNull, reason: 'v$version activity');
+        expect(s.stepsInc, isNull, reason: 'v$version stepsInc');
+      }
+    });
   });
 
   // ── 4. parseRealtimeHr reads every declared R-R slot ─────────────────────
@@ -251,6 +264,43 @@ void main() {
     });
   });
 
+  // ── 4b. live.dart realtimeRr shares the same physiological RR bound ──────
+  group('realtimeRr is bounded like parseRealtimeHr', () {
+    test('out-of-range slot values are dropped, in-range ones kept', () {
+      // 5ms (12,000bpm) and 3000ms are outside kMinRrMs..kMaxRrMs; a
+      // misaligned/corrupted 0x28 frame must not hand these to live HRV
+      // compute just because realtimeRr forgot the bound control.dart and
+      // records.dart both apply.
+      final f = _realtimeHrFrame(
+        ts: 1775395266,
+        hr: 62,
+        declaredCount: 4,
+        rrMs: [800, 5, 3000, 830],
+      );
+      expect(realtimeRr(_hex(f))!.rrMs, [800, 830]);
+    });
+
+    test('a frame with only out-of-range values yields no result at all', () {
+      final f = _realtimeHrFrame(
+        ts: 1775395266,
+        hr: 62,
+        declaredCount: 2,
+        rrMs: [5, 32000],
+      );
+      expect(realtimeRr(_hex(f)), isNull);
+    });
+
+    test('it still agrees with parseRealtimeHr once both are bounded', () {
+      final f = _realtimeHrFrame(
+        ts: 1775395266,
+        hr: 62,
+        declaredCount: 4,
+        rrMs: [800, 5, 3000, 830],
+      );
+      expect(realtimeRr(_hex(f))!.rrMs, parseRealtimeHr(f)!.rrMs);
+    });
+  });
+
   // ── 5. GET_ALARM_TIME dispatches on the on-wire alarm form ───────────────
   group('GET_ALARM_TIME form dispatch', () {
     const epoch = 1775395266;