Document the July batch in the changelog and README

Changelog entries for the Live Activity, mid-workout library adds,
backups, diagnostics, watch-only Health recording, navigation and
accessibility improvements, and the bug fixes; README key features
updated to match.

Claude-Session: https://claude.ai/code/session_01HJDQQDA9QdP8zByg43H5v3

CHANGELOG.md

@@ -1,5 +1,29 @@
 **July 2026**
 
+A Live Activity now shows your current exercise, set, and rest countdown on the Lock Screen and in the Dynamic Island.
+
+Any exercise from the library can now be added mid-workout, planned from your last time doing it.
+
+Settings now offers Backups — create snapshots of all your data and restore one with a tap.
+
+A new Diagnostics screen in Settings shows iCloud, document, and network status when sync seems off.
+
+Recording to Apple Health is now handled entirely by the watch, ending occasional duplicate workouts in Health.
+
+Starting a new workout now takes you straight into it instead of back to the list.
+
+The workout summary's heart-rate zone bar gains a numbered legend.
+
+VoiceOver now describes exercise checkboxes, heart-rate zones, and dates naturally, and workout timers scale with your preferred text size.
+
+The Bodyweight Core starter split no longer lists Bird Dog twice — Crunch takes the second slot.
+
+Deleting your last split on the phone now clears the watch too.
+
+Editing an old completed workout no longer moves its finish date to today.
+
+Traveling across time zones no longer leaves a duplicate copy of a workout behind.
+
 Exercise rows in a workout have a cleaner layout — the weight sits beside the exercise name, with sets × reps and any recorded machine settings beneath.
 
 The Splits and Exercises entries in Settings now show how many each contains.