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

Exercise Library/SYSTEM.md

@@ -79,6 +79,11 @@ never touches a motion script** — proportions are the skeleton's problem.
   proportions. Face-on machines (abductor/adductor, rotary torso) author
   genuine abduction or spine rotation and let projection do the rest. The
   camera can also orbit while the motion loops (`--orbit`).
+- **Elevation** — the default viewpoint pitches down 10° (`CAMERA_PITCH`;
+  override per motion via `"camera": {"pitch": ...}`), so the floor reads as
+  a plane — drawn as a rectangle — and near/far contacts straddle it.
+  Elevation is pure presentation: pins solve in the flat authored view and
+  the *posed* body tilts, so authored canvas targets never go out of reach.
 - **Feet** — each leg ends in a foot bone off the ankle. Dorsiflexion 0 keeps
   the foot perpendicular to the shin (right for standing, seated machines,
   planks); kneeling poses trail it back (−55), raises point it.