Slowly orbit the camera around prop-free form guides

Bodyweight motions (no equipment layer, no hide list) now turn the
camera a full revolution every 24 seconds while the motion loops, so
the exercise reads from every side; machine exercises keep their
authored view, since scene equipment is a view-locked billboard and a
hide list describes a single viewpoint.

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

Workouts/ExerciseFigure/MotionSolver.swift

@@ -499,8 +499,9 @@ struct MotionTimeline {
         return resolved[0]
     }
 
-    /// The drawable geometry at wall-clock `time`.
-    func geometry(at time: Double) -> FigureGeometry {
-        MotionSolver.frameGeometry(frame(at: time), prof: profile, cam: cam).1
+    /// The drawable geometry at wall-clock `time`. `yawOffset` turns the camera past
+    /// the exercise's authored yaw — the slow-orbit presentation.
+    func geometry(at time: Double, yawOffset: Double = 0) -> FigureGeometry {
+        MotionSolver.frameGeometry(frame(at: time), prof: profile, cam: cam + yawOffset).1
     }
 }