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/Lunge.motion.json

@@ -0,0 +1,30 @@
+{
+  "name": "Lunge",
+  "primary": 2,
+  "camera": {"zoom": 0.7},
+  "working": ["leg_r", "leg_l"],
+  "frames": [
+    {
+      "hold": 0.4, "tween": 1.0,
+      "root": {"pos": [160, 68], "pitch": 6},
+      "spine": [0, 0],
+      "neck": 2, "head": -6,
+      "shoulder_r": 5, "elbow_r": 8,
+      "shoulder_l": 5, "elbow_l": 8,
+      "hip_r": 25, "knee_r": 10, "ankle_r": 5,
+      "hip_l": -25, "knee_l": 10, "ankle_l": -12,
+      "pins": {"foot_r": [196, 148], "foot_l": [124, 147]}
+    },
+    {
+      "hold": 0.4, "tween": 1.0,
+      "root": {"pos": [160, 106], "pitch": 8},
+      "spine": [0, 0],
+      "neck": 2, "head": -6,
+      "shoulder_r": 5, "elbow_r": 8,
+      "shoulder_l": 5, "elbow_l": 8,
+      "hip_r": 80, "knee_r": 95, "ankle_r": 15,
+      "hip_l": -12, "knee_l": 100, "ankle_l": -42,
+      "pins": {"foot_r": [196, 148], "foot_l": [124, 147]}
+    }
+  ]
+}