Ship the 47-exercise library in-app: export, fixtures, tests, docs

render.py --export bundles the 25 new motion rigs and info pages;
figure-fixtures.json regenerated for all 47 (the Swift solver reproduces
every new motion, including negative-y pins and the new prop uses). The
fixture count assertion moves to 47, and the no-bundled-motion test now
uses Treadmill - a permanent COVERAGE.md exclusion - since Bench Press
exists. 48 tests green; watch target builds. Coverage handoff complete -
TODO-coverage.md retired.

Claude-Session: https://claude.ai/code/session_01HJDQQDA9QdP8zByg43H5v3

Workouts/Resources/ExerciseMotions/Rear Delt Fly.info.md

@@ -0,0 +1,38 @@
+# Rear Delt Fly
+
+The reverse pec deck — facing the pad, arms sweep from the front out
+wide and back, hitting what pressing never touches.
+
+- **Category:** Main circuit
+- **Type:** Machine-based reverse fly
+- **Targets:** Rear delts, mid-back
+- **Prescription:** 3 × 12–15, light
+
+## Setup
+
+Set the handles to the rear-fly position and sit facing the pad, chest
+supported, handles together in front at shoulder height, arms long with
+soft elbows.
+
+## Execution
+
+1. Sweep both arms out and back as far as the shoulder blades allow.
+2. Pause with the arms wide, squeezing between the shoulder blades.
+3. Return forward under control without the stack touching down.
+
+## Cues
+
+- Lead with the knuckles, arms long — it's a sweep, not a row.
+- Chest glued to the pad; no leaning back for leverage.
+- Light weight, full arc — momentum defeats the rear delts instantly.
+
+## Common Mistakes
+
+- Bending the elbows into a rowing motion.
+- Loading too heavy and shortening the arc.
+- Shrugging the traps into the sweep.
+
+## Progression
+
+More reps and a longer pause out wide before more weight; the Face Pull
+covers the same territory from the cable stack.