spark 2.1.0 splat viewer tab with OS-fused gyro look-around

WebView-hosted Spark renderer (butterfly.spz demo scene), fixed camera
position, rotation driven by expo-sensors DeviceMotion (ROTATION_VECTOR /
CoreMotion xMagneticNorthZVertical) via injectJavaScript; web fallback
uses deviceorientation in an iframe. Tap to re-center yaw.

app/(tabs)/_layout.tsx

@@ -23,6 +23,13 @@ export default function TabLayout() {
           tabBarIcon: ({ color }) => <IconSymbol size={28} name="house.fill" color={color} />,
         }}
       />
+      <Tabs.Screen
+        name="splat"
+        options={{
+          title: 'Splat',
+          tabBarIcon: ({ color }) => <IconSymbol size={28} name="rotate.3d" color={color} />,
+        }}
+      />
       <Tabs.Screen
         name="explore"
         options={{

app/(tabs)/splat.tsx

@@ -0,0 +1,5 @@
+import { SplatViewer } from '@/components/splat-viewer';
+
+export default function SplatScreen() {
+  return <SplatViewer />;
+}