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/kinematics.py

@@ -231,12 +231,15 @@ def fk_limb(kind, attach, joint, lower, ankle, prof, parent, sigma):
     return [attach, knee, ank, toe]
 
 
-def pose(nf, prof, cam_yaw):
+def pose(nf, prof, cam_yaw, cam_pitch=0.0):
     """FK a normalized frame into view space (x right, y up, z toward the
-    camera; origin at the root anchor). Returns points, parent frames (for
-    IK inversion), the nose direction, and the lateral depth factor k."""
+    camera; origin at the root anchor). `cam_pitch` tilts the viewpoint down
+    from slightly above (the scene rotates about the root). Returns points,
+    parent frames (for IK inversion), the nose direction, and the lateral
+    depth factor k."""
     r = nf["root"]
-    f_root = chain(rot_y(-cam_yaw), rot_y(r["yaw"]), rot_z(-r["pitch"]), rot_x(r["roll"]))
+    f_root = chain(rot_x(cam_pitch), rot_y(-cam_yaw),
+                   rot_y(r["yaw"]), rot_z(-r["pitch"]), rot_x(r["roll"]))
     origin = (0.0, 0.0, 0.0)
 
     s1, s2 = nf["spine"]
@@ -328,12 +331,12 @@ def view_from_canvas(pt, anchor, depth):
     return (pt[0] - anchor[0], anchor[1] - pt[1], depth)
 
 
-def resolve(nf, prof, cam_yaw):
+def resolve(nf, prof, cam_yaw, cam_pitch=0.0):
     """Pose a normalized frame and apply pins: for each pinned limb, solve IK
     against the canvas target (at the limb's FK depth), write the solved
     anatomical angles back into the frame, and re-pose. Returns
     (frame with IK-resolved angles, pose dict)."""
-    p = pose(nf, prof, cam_yaw)
+    p = pose(nf, prof, cam_yaw, cam_pitch)
     anchor = nf["root"]["pos"]
     solved = False
     for limb, (attach_key, sigma, pin) in LIMBS.items():
@@ -356,7 +359,7 @@ def resolve(nf, prof, cam_yaw):
             nf["hip_" + side], nf["knee_" + side] = upper, lower
         solved = True
     if solved:
-        p = pose(nf, prof, cam_yaw)
+        p = pose(nf, prof, cam_yaw, cam_pitch)
     return nf, p