Replace the YAML exercise catalogs with the motion-rig exercise library

The exercise picker now lists the bundled exercise library — the
motion-rig exercises exported from Exercise Library/ — instead of the
two *.exercises.yaml starter catalogs. ExerciseListLoader and the Yams
dependency are removed; ExerciseMotionLibrary gains exerciseNames, the
bundle enumeration the picker reads.

CHANGELOG.md

@@ -1,5 +1,7 @@
 **July 2026**
 
+Adding an exercise to a split now picks from the app's exercise library — the moves with animated form guides — replacing the old gym-machine and bodyweight starter lists.
+
 Starter routines now appear automatically the first time you use the app, instead of waiting behind a button in Settings.
 
 Editing a starter split now turns it into your own copy, so the built-in version can always be brought back later.