feat(Composite): Enhance root and child rendering with error differentiation

- Adjusted Composite to conditionally check for both direct root and child rendering.
- Differentiated error states: omitting an error when `component` prop is absent but showing an error when it's undefined.
- Fixed rendering of @app in the messages stream.

src/routes/+page.svelte

@@ -6,7 +6,7 @@
 	let composite = {
 		id: 'composite',
 		layout: {
-			areas: `   
+			areas: `
 				"top top top"
 				"main main main"
 				"footer footer footer";