Give cross-body bars a true 3D axis and fix the goblet squat hold

The orbit was always a real camera orbit — figure and props share one
rigid rotation — but a bar's screen-space angle authored the wrong 3D
rod: the default horizontal encoded a rod along the body axis, so
barbells hovered fixed on screen and vanished at the head-on view
where they should span widest. Line props now take "axis": "z" (both
renderers in lockstep, fixture-pinned): the world left-right direction
projects through the camera pitch like the floor quad — end-on plates
in profile, full span face-on, swinging with the hands in between.
Applied to the ten cross-body bars; vertical handles were already
orbit-invariant.

Goblet Squat's hand pins sat so close to the shoulders that the
two-bone IK was degenerate, flipping between a chicken-wing and an
elbow-behind solve; re-pinned level with the shoulders so the elbows
tuck straight down through the whole rep.

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

Workouts/Resources/ExerciseMotions/Barbell Squat.motion.json

@@ -4,7 +4,7 @@
   "camera": {"zoom": 0.7},
   "working": ["leg_r", "leg_l"],
   "props": [
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 14}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 14}
   ],
   "frames": [
     {

Workouts/Resources/ExerciseMotions/Bench Press.motion.json

@@ -8,7 +8,7 @@
       {"kind": "line", "pts": [[78, 129], [78, 150]], "w": 4},
       {"kind": "line", "pts": [[144, 129], [144, 150]], "w": 4}
     ]},
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 12}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 12}
   ],
   "frames": [
     {

Workouts/Resources/ExerciseMotions/Deadlift.motion.json

@@ -4,7 +4,7 @@
   "camera": {"zoom": 0.7},
   "working": ["leg_r", "leg_l", "spine"],
   "props": [
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 16}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 16}
   ],
   "frames": [
     {

Workouts/Resources/ExerciseMotions/Goblet Squat.motion.json

@@ -12,24 +12,24 @@
       "root": {"pos": [160, 66], "pitch": 5},
       "spine": [0, 0],
       "neck": 2, "head": -6,
-      "shoulder_r": 38, "elbow_r": 125,
-      "shoulder_l": 38, "elbow_l": 125,
+      "shoulder_r": 5, "elbow_r": 140,
+      "shoulder_l": 5, "elbow_l": 140,
       "hip_r": 5, "knee_r": 4, "ankle_r": 0,
       "hip_l": 5, "knee_l": 4, "ankle_l": 0,
       "pins": {"foot_r": [162, 148], "foot_l": [166, 150],
-               "hand_r": [176, -2], "hand_l": [180, 0]}
+               "hand_r": [185, -8], "hand_l": [189, -6]}
     },
     {
       "hold": 0.4, "tween": 1.0,
       "root": {"pos": [150, 104], "pitch": 22},
       "spine": [0, -4],
       "neck": 4, "head": -18,
-      "shoulder_r": 46, "elbow_r": 120,
-      "shoulder_l": 46, "elbow_l": 120,
+      "shoulder_r": 15, "elbow_r": 135,
+      "shoulder_l": 15, "elbow_l": 135,
       "hip_r": 96, "knee_r": 116, "ankle_r": 20,
       "hip_l": 96, "knee_l": 116, "ankle_l": 20,
       "pins": {"foot_r": [162, 148], "foot_l": [166, 150],
-               "hand_r": [190, 40], "hand_l": [194, 42]}
+               "hand_r": [196, 36], "hand_l": [200, 38]}
     }
   ]
 }

Workouts/Resources/ExerciseMotions/Hip Thrust.motion.json

@@ -7,7 +7,7 @@
       {"kind": "line", "pts": [[50, 122], [88, 122]], "w": 9, "depth": 8},
       {"kind": "line", "pts": [[68, 127], [68, 150]], "w": 5}
     ]},
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 13}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 13}
   ],
   "frames": [
     {

Workouts/Resources/ExerciseMotions/Incline Bench Press.motion.json

@@ -9,7 +9,7 @@
       {"kind": "line", "pts": [[140, 130], [166, 127]], "w": 8, "depth": 8},
       {"kind": "line", "pts": [[152, 133], [152, 150]], "w": 5}
     ]},
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 12}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 12}
   ],
   "frames": [
     {

Workouts/Resources/ExerciseMotions/Lat Pull Down.motion.json

@@ -9,7 +9,7 @@
       {"kind": "circle", "c": [272, 19], "r": 4, "fill": true, "color": "prop"}
     ]},
     {"type": "cable", "from": [272, 19], "to": ["hand_r", "hand_l"], "w": 4},
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 24}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 24}
   ],
   "frames": [
     {

Workouts/Resources/ExerciseMotions/Pull-Up.motion.json

@@ -4,7 +4,7 @@
   "camera": {"zoom": 0.7},
   "working": ["arm_r", "arm_l"],
   "props": [
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 24}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 24}
   ],
   "frames": [
     {

Workouts/Resources/ExerciseMotions/Romanian Deadlift.motion.json

@@ -4,7 +4,7 @@
   "camera": {"zoom": 0.7},
   "working": ["leg_r", "leg_l", "spine"],
   "props": [
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 13}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 26, "plateR": 13}
   ],
   "frames": [
     {

Workouts/Resources/ExerciseMotions/Shoulder Press.motion.json

@@ -9,7 +9,7 @@
       {"kind": "line", "pts": [[126, 143], [126, 151]], "w": 5},
       {"kind": "line", "pts": [[110, 151], [142, 151]], "w": 4, "depth": 5}
     ]},
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 10}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 10}
   ],
   "frames": [
     {

Workouts/Resources/ExerciseMotions/Triceps Pushdown.motion.json

@@ -8,7 +8,7 @@
       {"kind": "circle", "c": [186, -58], "r": 4, "fill": true, "color": "prop"}
     ]},
     {"type": "cable", "from": [186, -58], "to": ["hand_r", "hand_l"], "w": 3},
-    {"type": "bar", "at": ["hand_r", "hand_l"], "halfLen": 10}
+    {"type": "bar", "axis": "z", "at": ["hand_r", "hand_l"], "halfLen": 10}
   ],
   "frames": [
     {