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/Reverse Crunch.info.md

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+# Reverse Crunch
+
+Curl the pelvis toward the ribs — lower-ab flexion without neck strain.
+
+- **Category:** Main circuit
+- **Type:** Spinal flexion (lower)
+- **Targets:** Lower rectus abdominis, deep core
+- **Prescription:** 3 × 12–15 reps, controlled negative
+
+## Setup
+
+Lie on your back, knees bent toward the chest, shins roughly parallel to the
+floor, arms along your sides pressing lightly into the floor.
+
+## Execution
+
+1. Exhale and curl the pelvis up and toward the ribs, lifting the hips off the
+   floor — knees travel toward the chin.
+2. Pause briefly at the top.
+3. Lower the hips back down slowly, one vertebra at a time.
+
+## Cues
+
+- Curl, don't kick: the knees drifting up should come from the pelvis tilting,
+  not from leg swing.
+- Controlled negative — resist gravity all the way down.
+- Keep the head and shoulders relaxed on the floor.
+
+## Common Mistakes
+
+- Swinging the legs and lifting with momentum.
+- Pushing hard through the arms instead of the abs.
+- Letting the hips drop back down in one piece.
+
+## Progression
+
+Feet-elevated pelvic tilts → reverse crunch → slow 3-count negatives →
+incline (head-up) reverse crunch → dragonflag negatives