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/Dumbbell Curl/motion.json

@@ -0,0 +1,34 @@
+{
+  "name": "Dumbbell Curl",
+  "primary": 2,
+  "camera": {"zoom": 0.7},
+  "working": ["arm_r", "arm_l"],
+  "props": [
+    {"type": "dumbbell", "at": "hand_r"},
+    {"type": "dumbbell", "at": "hand_l"}
+  ],
+  "frames": [
+    {
+      "hold": 0.4, "tween": 1.0,
+      "root": {"pos": [160, 64], "pitch": 3},
+      "spine": [0, 0],
+      "neck": 2, "head": -4,
+      "shoulder_r": 3, "elbow_r": 10,
+      "shoulder_l": 3, "elbow_l": 10,
+      "hip_r": 3, "knee_r": 2, "ankle_r": 0,
+      "hip_l": 3, "knee_l": 2, "ankle_l": 0,
+      "pins": {"foot_r": [158, 148], "foot_l": [162, 150]}
+    },
+    {
+      "hold": 0.4, "tween": 1.2,
+      "root": {"pos": [160, 64], "pitch": 3},
+      "spine": [0, 0],
+      "neck": 2, "head": -4,
+      "shoulder_r": 6, "elbow_r": 128,
+      "shoulder_l": 6, "elbow_l": 128,
+      "hip_r": 3, "knee_r": 2, "ankle_r": 0,
+      "hip_l": 3, "knee_l": 2, "ankle_l": 0,
+      "pins": {"foot_r": [158, 148], "foot_l": [162, 150]}
+    }
+  ]
+}