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

WorkoutsTests/ExerciseMotionTests.swift

@@ -80,23 +80,30 @@ struct ExerciseMotionTests {
         #expect(hypot(releasedHand.x - releasedHand0.x, releasedHand.y - releasedHand0.y) > 1)
     }
 
-    /// Prop-free bodyweight motions slowly orbit the camera while looping; motions
-    /// with equipment keep their authored view (until machines orbit too).
-    @Test func orbitAppliesOnlyToPropFreeMotions() throws {
-        let birdDog = try #require(FigureAnimation(exerciseName: "Bird Dog"))
-        #expect(birdDog.orbits)
+    /// Every motion slowly orbits the camera while looping — bodyweight moves and
+    /// machines alike, since the equipment layer rotates with the figure.
+    @Test func everyMotionOrbits() throws {
         // 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 birdDog = try #require(FigureAnimation(exerciseName: "Bird Dog"))
         let head0 = birdDog.geometry(at: 0).headCenter
-        let head1 = birdDog.geometry(at: duration * 2).headCenter
+        let head1 = birdDog.geometry(at: birdDog.timeline.duration * 2).headCenter
         #expect(hypot(head0.x - head1.x, head0.y - head1.y) > 1)
 
+        // A machine orbits too, and its equipment turns with the figure: the seat
+        // slab's projected points move between the same two loop phases.
         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)
+        let geo0 = legPress.geometry(at: 0)
+        let geo1 = legPress.geometry(at: legPress.timeline.duration * 2)
+        #expect(hypot(geo0.headCenter.x - geo1.headCenter.x,
+                      geo0.headCenter.y - geo1.headCenter.y) > 1)
+        guard case .poly(let seat0, _, _) = geo0.propsBackground.first,
+              case .poly(let seat1, _, _) = geo1.propsBackground.first,
+              let s0 = seat0.first, let s1 = seat1.first else {
+            Issue.record("expected the Leg Press backrest slab as the first background prop")
+            return
+        }
+        #expect(hypot(s0.x - s1.x, s0.y - s1.y) > 1)
     }
 
     /// Every exported motion in the bundle decodes and builds a playable timeline.