Adjust rest time from the watch with the same 1-second stepper

A gear on the watch root opens a small Settings sheet whose stepper
edits the shared restSeconds default (10-180s, 1s steps). Edits ride a
new settingsUpdate message to the phone - debounced per stepper burst,
falling back to transferUserInfo when unreachable - which clamps the
value, writes the shared default, and re-echoes it to every device
through the application context. While an edit is pending on the watch,
an in-flight context's stale rest value is skipped so it can't yank the
stepper back mid-edit.

README.md

@@ -86,8 +86,9 @@ your own iCloud Drive.
   exercise, and run it as a paged flow: a **Ready?** lead-in, count-up work phases,
   count-down rests with final-three-second haptics and auto-advance, and a **Finish**
   page with **One More** and a **Done** that auto-completes after a countdown. A
-  phase-dot row (purple work, teal rest) tracks progress. Rest time and the
-  auto-finish countdown are configurable; changes sync back to the phone.
+  phase-dot row (purple work, teal rest) tracks progress. A Settings sheet on the
+  watch adjusts the rest time in 1-second steps; the change syncs back to the
+  phone, which echoes it to every device.
 - **Two-way live run** — prop your iPhone up during an Apple Watch workout and it runs
   the same Ready → work/rest → Finish flow with live timers, in step with the watch. It's
   bidirectional: drive from either device — swipe ahead, finish a set, add one — and the