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>

docs/adr/0030-halkyon-train.md

@@ -696,8 +696,8 @@ Strava. What was found, 27 Oct:
   sealed, so lines written meanwhile wait; the schedule is the phone's, for the last
   person whose app opened with a band, and *Let the band go* stops it. Polar's
   NONREM12 and NONREM3 are shown as light and deep sleep; the chart draws each 24/7
-  measurement's mean at its start; a night's times show in the phone's time zone. Not
-  yet tried with a Loop: whether the SDK's deletion includes its `until` day, and
+  measurement's mean at its start (a point a minute since D65); a night's times show
+  in the phone's time zone. Not yet tried with a Loop: whether the SDK's deletion includes its `until` day, and
   whether the job connects to the band in the background, are for a real band.
 
 - **D39 The Loop's training sessions are workouts** (recommended, the developer's; 28
@@ -1731,6 +1731,19 @@ Strava. What was found, 27 Oct:
     provider takes one from `MAP_DARK_STYLE_URL` (HTTPS, else none: the light style
     in both themes). A dark Liberty made in the app (its colours inverted) was the
     alternative, a style of the app's own for a provider's tiles it can't know.
+  - **The day's charts**: the skin temperature was drawn backwards in places, as the
+    band's samples aren't always in time order and nothing sorted them; they are
+    sorted, a time given twice kept once, as the Loop's lines are read and as a kept
+    day is opened (`skinInOrder`), and every line chart (`WorkoutChart`) draws its
+    points in the order of their x and spans their least to their most
+    (`chartInOrder`). The heart rate spiked down: the band writes 0 where it lost
+    contact, and a run's mean counted those in. A value that isn't a heart's rate
+    (0, or beyond 250) is 0, none read, as the lines are read, kept in its place so
+    the samples after keep their times, and left out of every mean, also of days
+    kept before. The chart draws the samples themselves a point a minute, averaged
+    across runs (`heartByMinute`, a second between a run's samples), not one mean a
+    run, which zigzagged where runs lay close. Dropping the zeros from the list was
+    the alternative; it would have moved the later samples' times.
 ## Consequences
 
 - Train's sensors are one pattern: open profiles read by the app itself, on the phone;