Bring back the big timer; the bar pill takes over on scroll

The big asleep/awake card returns below the frozen bar, and the bar
pill becomes its twin: both tick together, but the pill stays
visibility-hidden — slot reserved, so the bar never shifts — while the
card is on screen, appearing only once the card scrolls out of sight
(rAF-throttled scroll check against the bar's bottom edge).

src/changelog.json

@@ -1,4 +1,5 @@
 [
+  { "date": "2026-07-13", "text": "The big timer is back at the top — scroll past it and it hops into the frozen bar instead" },
   { "date": "2026-07-13", "text": "The top bar fits on one row: timer, day arrows, date picker and Today" },
   { "date": "2026-07-13", "text": "Pick how many days the charts cover — 7, 14 or 30 (default 7)" },
   { "date": "2026-07-13", "text": "Much finer y-axis on the food chart" },