fix(train): a day's skin temperature in time order, and its heart rate a point a minute without lost contact

The skin temperature's line ran backwards in places: the band's samples
aren't always in time order, and neither the Loop's lines, nor the kept
day, nor the chart sorted them. They are sorted now, a time given twice
kept once, as the lines are read and as a kept day is opened, and
WorkoutChart draws any points in the order of their x, from the least
to the most.

The heart rate spiked down: the band writes 0 where it lost contact,
and each run's mean, the chart's one point a run, counted those in. A
value that isn't a heart's rate is 0, none read, in its place (so the
samples after keep their times), left out of every mean, days kept
before included; the chart draws the samples a point a minute, averaged
across runs, rather than one mean a run, which zigzagged where runs lay
close. ADR 0030, D65.

Whats-New: A day's skin temperature no longer runs backwards, and its heart rate no longer drops where the band lost contact.
Whats-New-De: Die Hauttemperatur eines Tages läuft nicht mehr rückwärts, und sein Puls fällt nicht mehr ab, wo das Band den Kontakt verlor.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/train/halkyon_train_flutter/test/feature/day/day_heart_test.dart

@@ -0,0 +1,63 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_train_flutter/src/feature/day/model/day.dart';
+
+/// A day's 24/7 heart rate as its chart draws it (ADR 0030, D37, D65): the
+/// samples a point a minute, what the band couldn't read left out.
+void main() {
+  test("a run's mean leaves out what the band couldn't read", () {
+    const run = HeartRun(
+      at: Duration.zero,
+      trigger: HeartTrigger.timed,
+      bpm: [70, 0, 72, 0],
+    );
+    const none = HeartRun(
+      at: Duration.zero,
+      trigger: HeartTrigger.timed,
+      bpm: [0, 0],
+    );
+
+    expect(run.mean, 71);
+    expect(none.mean, isNull);
+  });
+
+  test('the samples come a point a minute, averaged across runs, in time '
+      'order, half a run lost contact or not', () {
+    const at = Duration(hours: 7, minutes: 30);
+    final points = heartByMinute([
+      // Later, a run of its own.
+      HeartRun(
+        at: at + const Duration(minutes: 10),
+        trigger: HeartTrigger.highActivity,
+        bpm: const [140, 142],
+      ),
+      // Two minutes a sample a second, every other one not read.
+      HeartRun(
+        at: at,
+        trigger: HeartTrigger.timed,
+        bpm: [
+          for (var i = 0; i < 120; i++)
+            if (i.isOdd) 0 else if (i < 60) 60 else 64,
+        ],
+      ),
+      // Within the first minute too.
+      HeartRun(
+        at: at + const Duration(seconds: 50),
+        trigger: HeartTrigger.manual,
+        bpm: const [90],
+      ),
+      // Nothing read at all.
+      HeartRun(
+        at: at + const Duration(minutes: 20),
+        trigger: HeartTrigger.timed,
+        bpm: const [0, 0, 0],
+      ),
+    ]);
+
+    expect(points, [
+      // 30 samples of 60 and one of 90.
+      (at, 61),
+      (at + const Duration(minutes: 1), 64),
+      (at + const Duration(minutes: 10), 141),
+    ]);
+  });
+}

apps/train/halkyon_train_flutter/test/feature/day/day_payload_test.dart

@@ -65,6 +65,25 @@ void main() {
     expect(decodeHeart(encodeHeart(heart)), heart);
   });
 
+  test('a day kept with its skin temperature out of order comes back in '
+      'order, a time given twice once (D65)', () {
+    final kept = DayContent(
+      date: date,
+      skin: const [
+        (Duration(minutes: 2), 33.5),
+        (Duration.zero, 33.1),
+        (Duration(minutes: 1), 33.3),
+        (Duration.zero, 33.1),
+      ],
+    );
+
+    expect(decodeDay(encodeDay(kept))!.skin, const [
+      (Duration.zero, 33.1),
+      (Duration(minutes: 1), 33.3),
+      (Duration(minutes: 2), 33.5),
+    ]);
+  });
+
   test('a day with nothing but its date comes back so', () {
     final bare = DayContent(date: date);
 

apps/train/halkyon_train_flutter/test/feature/day/loop_lines_test.dart

@@ -188,6 +188,48 @@ void main() {
     },
   );
 
+  test('skin temperature comes in time order, a time given twice once '
+      '(D65)', () {
+    final lines = LoopLines()
+      ..add(const {
+        'kind': 'skin',
+        'date': '2026-10-28',
+        'samples': [
+          [120000, 33.5],
+          [0, 33.1],
+          [60000, 33.3],
+          [0, 40.0],
+          [60000, 33.3],
+        ],
+      });
+
+    expect(lines.skins[today], const [
+      (Duration.zero, 33.1),
+      (Duration(minutes: 1), 33.3),
+      (Duration(minutes: 2), 33.5),
+    ]);
+  });
+
+  test("heart rate the band couldn't read, 0 or beyond a heart's, counts "
+      'as none read, in its place (D65)', () {
+    final lines = LoopLines()
+      ..add(const {
+        'kind': 'heart',
+        'date': '2026-10-27',
+        'runs': [
+          {
+            'at': 600,
+            'trigger': 'timed',
+            'bpm': [60, 0, 62, 0, 300, -1],
+          },
+        ],
+      });
+
+    final run = lines.hearts[yesterday]!.single;
+    expect(run.bpm, [60, 0, 62, 0, 0, 0]);
+    expect(run.mean, 61);
+  });
+
   test('a later line of a kind and date replaces an earlier one', () {
     final lines = LoopLines()
       ..add(summary)

apps/train/halkyon_train_flutter/test/feature/workout/workout_chart_test.dart

@@ -24,6 +24,21 @@ void main() {
     ),
   );
 
+  test('its points are drawn in the order of their x, never backwards '
+      '(D65); points in order are taken as they are', () {
+    const sorted = [(x: 0.0, value: 1.0), (x: 1.0, value: 2.0)];
+
+    expect(
+      chartInOrder(const [
+        (x: 2.0, value: 3.0),
+        (x: 0.0, value: 1.0),
+        (x: 1.0, value: 2.0),
+      ]),
+      [(x: 0.0, value: 1.0), (x: 1.0, value: 2.0), (x: 2.0, value: 3.0)],
+    );
+    expect(identical(chartInOrder(sorted), sorted), isTrue);
+  });
+
   testWidgets('held, the value and its moment under the finger show beside '
       'the title, following the finger, and go when it lifts', (
     tester,