Suspend watch edit locks on background; degrade oversized pushes

Two watch-stranding fixes (BULLETPROOFING.md M1, M4):

The exclusive-edit lock rode in the latest-wins context and was cleared
only by onDisappear, so an editor left open in a pocketed (or
force-quit) phone parked the watch's run indefinitely ("Editing on
iPhone..."). The scene-phase hook now publishes the locks as cleared
while the app is backgrounded - without forgetting them locally - and
re-asserts them on return to the foreground.

pushAll treated a failed updateApplicationContext as log-only, so a
payload past WatchConnectivity's size ceiling silently froze the watch
out of all future state. A failed push now retries with the
recently-completed tail dropped (display-only on the watch); only a
failure of the slim push too remains an error.

Claude-Session: https://claude.ai/code/session_01PVNBVKp5bcq52X722uMjwT

CHANGELOG.md

@@ -8,6 +8,10 @@ A recording cut short by watchOS itself is now still saved to Apple Health inste
 
 Ending a workout and immediately starting a new one no longer risks a stray seconds-long workout appearing in Apple Health.
 
+Putting the iPhone away with an editor still open no longer leaves the workout stuck showing Editing on iPhone on the watch.
+
+Syncing to the watch no longer silently stops when a large workout history makes the update too big to send.
+
 A new Cardio exercise and matching starter split let you log aerobic sessions, tracked on your Apple Watch as a cardio workout.
 
 A new Auto-Advance option lets a split flow hands-free from one exercise to the next, resting automatically between them.