Add a live status panel between the run screen's halves

Replaces the small target-HR pill on the iPhone run screen with a
glanceable big-digit strip between the timer flow and the figure —
heart rate (band-tinted with the cue arrow when the run carries a
target), HR zone, active calories, and the workout stopwatch. A
horizontal band in portrait, a vertical column in landscape (the
inverse of the half-and-half split, so it always sits between them).

The watch now rides the running calorie total and the HR zone (1-5,
computed watch-side where max HR is known) along with each live HR
sample; absent keys keep older builds wire-compatible both ways.
LiveRunState holds all three under the shared staleness expiry. The
screenshot rig seeds believable values so the run capture shows the
panel populated.

CHANGELOG.md

@@ -1,5 +1,7 @@
 **July 2026**
 
+A live status panel between the timer and the figure now shows heart rate (with the target color cues, in much larger type), HR zone, calories, and workout time.
+
 A new Library tab puts your routines and the exercise library one tap away instead of buried in Settings.
 
 Drag routines into your own order — the Today board and routine pickers follow it everywhere.