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.

README.md

@@ -13,10 +13,9 @@ your own iCloud Drive.
   machine routines, plus an equipment-free **Bodyweight Core** circuit with its
   own warm-up) appear automatically on first launch; editing one makes it your
   own copy, and deleted starters can be restored from Settings.
-- **Exercise library** — a bundled catalog of starter exercises (bodyweight and
-  machine-based) to populate your splits, plus a growing reference library
-  (`Exercise Library/`) with per-exercise setup, cues, mistakes, progressions,
-  and a rig-animated stick-figure visual system.
+- **Exercise library** — a bundled library of exercises to populate your splits,
+  authored in `Exercise Library/` with per-exercise setup, cues, mistakes,
+  progressions, and a rig-animated stick-figure visual system.
 - **Run a workout** — start a session from a split, then tap an exercise to run it
   as a paged flow: a **Ready?** lead-in, count-up work phases, count-down rests, and
   a **Finish** page — mirroring the Apple Watch. Swipe a row to mark it complete, or