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 Shoulder Press/motion.json

@@ -0,0 +1,41 @@
+{
+  "name": "Dumbbell Shoulder Press",
+  "primary": 2,
+  "camera": {"zoom": 0.82},
+  "working": ["arm_r", "arm_l"],
+  "props": [
+    {"type": "scene", "shapes": [
+      {"kind": "line", "pts": [[117, 128], [113, 58]], "w": 8, "depth": 8},
+      {"kind": "line", "pts": [[114, 134], [150, 134]], "w": 8, "depth": 8},
+      {"kind": "line", "pts": [[132, 136], [132, 150]], "w": 5}
+    ]},
+    {"type": "dumbbell", "at": "hand_r"},
+    {"type": "dumbbell", "at": "hand_l"}
+  ],
+  "frames": [
+    {
+      "hold": 0.4, "tween": 1.0,
+      "root": {"pos": [130, 124], "pitch": 2},
+      "spine": [0, 2],
+      "neck": 4, "head": -6,
+      "shoulder_r": 35, "elbow_r": 145,
+      "shoulder_l": 35, "elbow_l": 145,
+      "hip_r": 84, "knee_r": 64,
+      "hip_l": 84, "knee_l": 64,
+      "pins": {"foot_r": [176, 150], "foot_l": [180, 151],
+               "hand_r": [146, 30], "hand_l": [150, 32]}
+    },
+    {
+      "hold": 0.4, "tween": 1.2,
+      "root": {"pos": [130, 124], "pitch": 2},
+      "spine": [0, 2],
+      "neck": 4, "head": -6,
+      "shoulder_r": 168, "elbow_r": 8,
+      "shoulder_l": 168, "elbow_l": 8,
+      "hip_r": 84, "knee_r": 64,
+      "hip_l": 84, "knee_l": 64,
+      "pins": {"foot_r": [176, 150], "foot_l": [180, 151],
+               "hand_r": [138, -19], "hand_l": [142, -17]}
+    }
+  ]
+}