Author the machine exercise circuit with props and corrected hip machine motions

Fourteen Planet Fitness machine exercises join the rig library, each with
authored motion, info page, and schematic equipment via the new props layer
(scene shapes, cables, bars, pads) rendered in lockstep by render.py and the
in-app figure renderer. Abductor and Adductor are authored face-on with the
real seated machine motion — knees-bent legs swinging apart/together against
knee pads — replacing the earlier middle-split depiction. The watch target
now bundles the figure renderer and motion rigs too.

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

Workouts/Resources/ExerciseMotions/Hollow Body Hold.info.md

@@ -0,0 +1,37 @@
+# Hollow Body Hold
+
+The gold standard for deep core tension — a shallow, rigid banana shape.
+
+- **Category:** Main circuit
+- **Type:** Anti-extension (isometric hold)
+- **Targets:** Rectus abdominis, deep core, hip flexors
+- **Prescription:** 3 × 20–40 s holds
+
+## Setup
+
+Lie on your back, arms extended overhead beside the ears, legs straight and
+together.
+
+## Execution
+
+1. Press the lower back *into* the floor and hold it there — this never releases.
+2. Lift shoulder blades and legs a few inches off the floor into a shallow
+   banana shape.
+3. Reach long through fingers and toes and hold.
+
+## Cues
+
+- The lower back stays welded to the floor; if it lifts, shorten the shape.
+- Chin gently tucked — look at your thighs, not the ceiling.
+- Lower = harder. Height is not the goal, tension is.
+
+## Common Mistakes
+
+- Lower back arching off the floor (the hold has failed at that point).
+- Folding at the hips into a V-sit.
+- Neck cranked forward doing all the "work".
+
+## Progression
+
+Tuck hold (knees in) → one leg extended → full extension, arms overhead →
+hollow rocks