Slowly orbit the camera around every form guide

With the equipment layer carrying world-space 3D form, the prop-free
gate comes off: machines now get the same slow orbit as the bodyweight
moves, their seats, cables, bars, and rollers turning with the figure.
Closes out the orbit-for-all-exercises plan.

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

Exercise Library/SYSTEM.md

@@ -77,7 +77,9 @@ never touches a motion script** — proportions are the skeleton's problem.
   side view, 90 views the figure face-on — real foreshortening, not faked
   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`).
+  camera also orbits while the motion loops (`--orbit`; the in-app renderer
+  slowly orbits **every** exercise, machines included — props have
+  world-space 3D form and turn with the figure).
 - **Elevation & the mat** — the default viewpoint pitches down 10°
   (`CAMERA_PITCH`; override per motion via `"camera": {"pitch": ...}`), and
   the ground is drawn as an **exercise mat**: a world-space quad sized to the