View the figure from a slight elevation and refine the leg-machine rollers

The default camera pitches down 10 degrees, so the floor reads as a
plane (drawn as a rectangle) and near/far contacts straddle it.
Elevation is pure presentation - IK pins solve in the flat authored
view and the posed body tilts, the same pattern as the orbit, so
authored canvas targets never go out of reach. The leg-extension
roller moves up onto the shin above the ankle and the leg-curl roller
tucks under the heel. Fixtures and reference test values regenerated
for the pitched camera.

Claude-Session: https://claude.ai/code/session_01LEoff8bXGBS83tK1c55Mf7

Workouts/Resources/ExerciseMotions/Leg Extension.motion.json

@@ -11,7 +11,7 @@
       {"kind": "line", "pts": [[104, 150], [166, 150]], "w": 5},
       {"kind": "circle", "c": [114, 90], "r": 3.5, "fill": true, "color": "prop"}
     ]},
-    {"type": "roller", "at": ["foot_r", "foot_l"], "side": 1, "r": 5, "back": -2}
+    {"type": "roller", "at": ["foot_r", "foot_l"], "side": 1, "r": 5, "back": 7}
   ],
   "frames": [
     {