feat(av-live-body): wire USB consumer to renderer

ContentView owns and starts a USBSkeletonConsumer, threaded
through BodyView into Skeleton3DRenderer.attach. The renderer
subscribes its $bodies into lastArkit, so the iPhone's USB
skeleton drives the on-screen 91-joint markers.

launcher/AV-Live-Body/Sources/AVLiveBody/AVLiveBodyApp.swift

@@ -67,17 +67,20 @@ struct ContentView: View {
     @StateObject private var poseListener = PoseOSCListener()
     @StateObject private var arkitListener = ArkitOSCListener()
     @StateObject private var dataFeeds = DataFeedsOSCListener()
+    @StateObject private var usbConsumer = USBSkeletonConsumer()
 
     var body: some View {
         ZStack(alignment: .topLeading) {
             BodyView(renderer: renderer, settings: settings,
                      poseListener: poseListener,
-                     arkitListener: arkitListener)
+                     arkitListener: arkitListener,
+                     usbConsumer: usbConsumer)
                 .onAppear {
                     renderer.startOSCServer()
                     poseListener.start()
                     arkitListener.start()
                     dataFeeds.start()
+                    usbConsumer.start()
                 }
                 .onReceive(NotificationCenter.default.publisher(
                     for: .toggleSettings)) { _ in

launcher/AV-Live-Body/Sources/AVLiveBody/BodyView.swift

@@ -13,6 +13,7 @@ struct BodyView: NSViewRepresentable {
     @ObservedObject var settings: RenderSettings
     @ObservedObject var poseListener: PoseOSCListener
     @ObservedObject var arkitListener: ArkitOSCListener
+    @ObservedObject var usbConsumer: USBSkeletonConsumer
 
     func makeNSView(context: Context) -> NSView {
         let container = NSView(frame: .zero)
@@ -109,7 +110,8 @@ struct BodyView: NSViewRepresentable {
         arView.scene.addAnchor(skel3dAnchor)
         let skel3d = Skeleton3DRenderer()
         skel3d.attach(to: skel3dAnchor, listener: poseListener,
-                      arkitListener: arkitListener)
+                      arkitListener: arkitListener,
+                      usbConsumer: usbConsumer)
         context.coordinator.skel3dAnchor = skel3dAnchor
         context.coordinator.skel3d = skel3d
         context.coordinator.keyLight = key

launcher/AV-Live-Body/Sources/AVLiveBody/Skeleton3DRenderer.swift

@@ -87,6 +87,7 @@ final class Skeleton3DRenderer: ObservableObject {
     private var faceSub: AnyCancellable?
     private var handSub: AnyCancellable?
     private var arkitSub: AnyCancellable?
+    private var usbSub: AnyCancellable?
     private var lastArkit: [Int: ArkitOSCListener.ArkitBodyFrame] = [:]
     private var lastUpdateAt: TimeInterval = 0
     /// Optional per-pid offset to align the skeleton with another
@@ -112,7 +113,8 @@ final class Skeleton3DRenderer: ObservableObject {
     /// Attach to a scene by giving it an AnchorEntity that owns all
     /// skeleton entities, and start observing the listener.
     func attach(to anchor: Entity, listener: PoseOSCListener,
-                arkitListener: ArkitOSCListener? = nil) {
+                arkitListener: ArkitOSCListener? = nil,
+                usbConsumer: USBSkeletonConsumer? = nil) {
         rootAnchor = anchor
         poseSub = listener.$body3d
             .receive(on: DispatchQueue.main)
@@ -136,6 +138,13 @@ final class Skeleton3DRenderer: ObservableObject {
                     Task { @MainActor in self?.lastArkit = frames }
                 }
         }
+        if let usb = usbConsumer {
+            usbSub = usb.$bodies
+                .receive(on: DispatchQueue.main)
+                .sink { [weak self] frames in
+                    Task { @MainActor in self?.lastArkit = frames }
+                }
+        }
     }
 
     func detach() {
@@ -147,6 +156,8 @@ final class Skeleton3DRenderer: ObservableObject {
         handSub = nil
         arkitSub?.cancel()
         arkitSub = nil
+        usbSub?.cancel()
+        usbSub = nil
         for (_, p) in persons { p.root.removeFromParent() }
         persons.removeAll()
         lastSeenAt.removeAll()