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

Exercise Library/Leg Press/info.md

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+# Leg Press
+
+The seated machine squat — maximum lower-body load with the back fully
+supported.
+
+- **Category:** Main circuit
+- **Type:** Machine-based compound push
+- **Targets:** Quadriceps, glutes, hamstrings
+- **Prescription:** 4 × 10
+
+## Setup
+
+Sit with your back and hips flat against the pad. Place your feet
+shoulder-width on the platform, heels never floating. Adjust the seat so your
+knees start near 90°.
+
+## Execution
+
+1. Press through your heels until your legs are nearly straight — stop short
+   of locking the knees.
+2. Pause briefly, then bend the knees to return under control.
+3. Keep your back and hips glued to the pad the whole rep.
+
+## Cues
+
+- Drive through the heels, not the toes.
+- Knees track over the feet — don't let them cave inward.
+- Lower back stays on the pad; if the hips curl up, you've gone too deep.
+
+## Common Mistakes
+
+- Locking the knees hard at the top.
+- Bouncing out of the bottom.
+- Letting the hips roll off the pad at the bottom of the rep.
+
+## Progression
+
+Add weight in small plates once all four sets of ten are controlled; single-leg
+presses for asymmetry work.