Rebuild the exercise figure on an anatomical 3D skeleton

The library's planar world-angle rig becomes a genuine 3D anatomical
model: skeleton.json holds bone-length profiles (real shoulder/pelvis
widths, feet, neutral/female/male) and per-joint ROM; motions pose
joints with anatomical angles (flexion/abduction/rotation from neutral
standing) under a per-exercise orthographic camera, resolved by
kinematics.py (3D FK, analytic two-bone IK with anatomical write-back)
and validated against physiological ranges. All 20 sagittal motions
were migrated by planar decomposition with 0.00 px golden parity against
the old renderer — relabeled to true anatomy, since shading is now
near-dark/far-light by camera depth rather than by limb suffix — and
the face-on machines are re-authored honestly: Abductor/Adductor with
real hip abduction (the foreshortened "frontal" profile is retired) and
Rotary with genuine spine axial rotation. Figures gain articulated
feet; profiles swap without touching a single motion script; --orbit
sweeps the camera 360° while a motion loops.

The in-app SwiftUI renderer (iOS + watch) is ported to the same model
and consumes the exported motions verbatim; figure-fixtures.json pins
its geometry to the Python pipeline within 0.5 px across every
exercise, key frame, tween, and orbit sample. Also makes the watch
bridge logger nonisolated for the newer SDK's stricter isolation
checking.

Claude-Session: https://claude.ai/code/session_01LEoff8bXGBS83tK1c55Mf7

README.md

@@ -14,7 +14,7 @@ your own iCloud Drive.
   own copy, and deleted starters can be restored from Settings.
 - **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 — covering the
+  progressions, and an anatomically-rigged 3D stick-figure visual system — covering the
   bodyweight core moves plus the full Planet Fitness–style machine circuit
   (presses, rows, pulldowns, curls, leg and hip machines).
 - **Run a workout** — start a session from a split, then tap an exercise to run it
@@ -24,10 +24,11 @@ your own iCloud Drive.
   from the **⋯** menu — **Save** keeps your progress (remaining exercises are marked
   skipped) or **Discard** removes it.
 - **Animated form guide** — every library exercise shows a looping stick-figure
-  demonstration on the run screen's bottom half, rendered live from the Exercise
+  demonstration on the run screen's bottom half, posed by real joint angles on an
+  anatomical 3D skeleton (complete with feet) and rendered live from the Exercise
   Library's rig data with the working limbs highlighted — machine exercises
   include schematic equipment (seats, bars, cables, roller pads) that moves with
-  the figure.
+  the figure, and face-on machines show true hip abduction and torso rotation.
 - **Machine comfort settings** — machine-based exercises remember your setup
   (seat height, back-rest position, pin position, …), shown on the workout
   screen and editable mid-workout; changes save back to the split for next time.