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

WorkoutsTests/ExerciseMotionTests.swift

@@ -74,6 +74,25 @@ struct ExerciseMotionTests {
         #expect(hypot(releasedHand.x - 105, releasedHand.y - 152) > 1)
     }
 
+    /// Prop-free bodyweight motions slowly orbit the camera while looping; motions with
+    /// equipment (view-locked scene shapes) or a hide list keep their authored view.
+    @Test func orbitAppliesOnlyToPropFreeMotions() throws {
+        let birdDog = try #require(FigureAnimation(exerciseName: "Bird Dog"))
+        #expect(birdDog.orbits)
+        // Same loop phase seconds apart: the orbit yaw differs, so the projected head
+        // moves even though the pose is identical.
+        let duration = birdDog.timeline.duration
+        let head0 = birdDog.geometry(at: 0).headCenter
+        let head1 = birdDog.geometry(at: duration * 2).headCenter
+        #expect(hypot(head0.x - head1.x, head0.y - head1.y) > 1)
+
+        let legPress = try #require(FigureAnimation(exerciseName: "Leg Press"))
+        #expect(!legPress.orbits)
+        let fixed0 = legPress.geometry(at: 0).headCenter
+        let fixed1 = legPress.geometry(at: legPress.timeline.duration * 2).headCenter
+        #expect(abs(fixed0.x - fixed1.x) < 1e-9 && abs(fixed0.y - fixed1.y) < 1e-9)
+    }
+
     /// Every exported motion in the bundle decodes and builds a playable timeline.
     @Test func allBundledMotionsBuildTimelines() throws {
         let urls = Bundle.main.urls(forResourcesWithExtension: "json", subdirectory: nil) ?? []