Fix REPL timeout with return statements by wrapping user code in function

- User code with return statement was exiting the async IIFE early
- Completion callbacks and window.complete() were never reached
- Now wrap user code in userCodeFunc to capture return value
- Return statement returns from userCodeFunc, not outer IIFE
- Completion callbacks and window.complete() always execute
- Return value is logged to console output
- Fixes 30-second timeout when using return statements in REPL

packages/web-ui/src/components/SandboxedIframe.ts

@@ -328,7 +328,17 @@ export class SandboxIframe extends LitElement {
 	<script type="module">
 		(async () => {
 			try {
-				${userCode}
+				// Wrap user code in async function to capture return value
+				const userCodeFunc = async () => {
+					${userCode}
+				};
+
+				const returnValue = await userCodeFunc();
+
+				// Log return value if present
+				if (returnValue !== undefined) {
+					console.log('Return value:', returnValue);
+				}
 
 				// Call completion callbacks before complete()
 				if (window.__completionCallbacks && window.__completionCallbacks.length > 0) {