Add the free-weight canon and bodyweight staples (16 exercises)

Squat/lunge: Barbell Squat, Goblet Squat, Bodyweight Squat, Lunge.
Bench station: Bench Press, Incline Bench Press, Dumbbell Bench Press,
Dumbbell Fly (the fly authors the face-on camera for its frontal arc).
Dumbbell rack: Dumbbell Row, Dumbbell Shoulder Press, Dumbbell Curl,
Lateral Raise - first uses of the dumbbell prop. Bodyweight: Push-Up,
Pull-Up, Crunch, Dip.

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

Exercise Library/Push-Up/motion.json

@@ -0,0 +1,31 @@
+{
+  "name": "Push-Up",
+  "primary": 1,
+  "working": ["arm_r", "arm_l"],
+  "frames": [
+    {
+      "hold": 0.4, "tween": 0.9,
+      "root": {"pos": [180, 115], "yaw": 180, "pitch": 73},
+      "spine": [0, 0],
+      "neck": 0, "head": -60,
+      "shoulder_r": 90, "elbow_r": 8,
+      "shoulder_l": 90, "elbow_l": 8,
+      "hip_r": 5, "knee_r": 3, "ankle_r": 25,
+      "hip_l": 5, "knee_l": 3, "ankle_l": 25,
+      "pins": {"hand_r": [97, 148], "hand_l": [101, 150],
+               "foot_r": [256, 143], "foot_l": [260, 145]}
+    },
+    {
+      "hold": 0.4, "tween": 0.9,
+      "root": {"pos": [180, 132], "yaw": 180, "pitch": 85},
+      "spine": [0, 0],
+      "neck": 0, "head": -55,
+      "shoulder_r": 60, "elbow_r": 110,
+      "shoulder_l": 60, "elbow_l": 110,
+      "hip_r": 5, "knee_r": 3, "ankle_r": 25,
+      "hip_l": 5, "knee_l": 3, "ankle_l": 25,
+      "pins": {"hand_r": [97, 148], "hand_l": [101, 150],
+               "foot_r": [256, 143], "foot_l": [260, 145]}
+    }
+  ]
+}