Expand Promise handling examples with comprehensive patterns

Add examples for async IIFEs, Promise.resolve with objects, and nested
async operations to demonstrate the full range of Promise patterns
supported in JavaScript/TypeScript code execution contexts.

These patterns are verified by the new tests in PR #246 and address
issue #206 where Promise-based code previously returned empty objects
instead of resolved values.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: github-actions[bot]

src/content/docs/sandbox/api/interpreter.mdx

@@ -98,14 +98,40 @@ When executing JavaScript or TypeScript code, if the last expression evaluates t
 ```
 const ctx = await sandbox.createCodeContext({ language: 'javascript' });
 
-const result = await sandbox.runCode(`
+// Async function
+const result1 = await sandbox.runCode(`
 async function fetchData() {
   return { status: 'success', value: 42 };
 }
 fetchData()
 `, { context: ctx });
-
-console.log(result.results[0].json); // { status: 'success', value: 42 }
+console.log(result1.results[0].json); // { status: 'success', value: 42 }
+
+// Async IIFE
+const result2 = await sandbox.runCode(`
+(async () => {
+  const value = await Promise.resolve(10);
+  return value * 2;
+})()
+`, { context: ctx });
+console.log(result2.results[0].json); // 20
+
+// Promise.resolve with objects
+const result3 = await sandbox.runCode(
+  'Promise.resolve({ status: "success", data: [1, 2, 3] })',
+  { context: ctx }
+);
+console.log(result3.results[0].json); // { status: "success", data: [1, 2, 3] }
+
+// Nested async operations
+const result4 = await sandbox.runCode(`
+(async () => {
+  const a = await Promise.resolve(10);
+  const b = await Promise.resolve(20);
+  return a + b;
+})()
+`, { context: ctx });
+console.log(result4.results[0].json); // 30
 ```
 </TypeScriptExample>