feat(companion): initial rn port scaffold

aris/app/_layout.tsx

@@ -0,0 +1,15 @@
+import "../global.css";
+
+import { Stack } from "expo-router";
+import { PortalHost } from "@rn-primitives/portal";
+
+export default function Layout() {
+	return (
+		<>
+			<Stack>
+				<Stack.Screen name="(tabs)" options={{ headerShown: false }} />
+			</Stack>
+			<PortalHost />
+		</>
+	);
+}