fix: handle unhandled promise rejection in vended CDK main()

Author: notgitika

src/assets/__tests__/__snapshots__/assets.snapshot.test.ts.snap

@@ -80,7 +80,10 @@ async function main() {
   app.synth();
 }
 
-main();
+main().catch((error: unknown) => {
+  console.error('AgentCore CDK synthesis failed:', error instanceof Error ? error.message : error);
+  process.exitCode = 1;
+});
 "
 `;
 

src/assets/cdk/bin/cdk.ts

@@ -47,4 +47,7 @@ async function main() {
   app.synth();
 }
 
-main();
+main().catch((error: unknown) => {
+  console.error('AgentCore CDK synthesis failed:', error instanceof Error ? error.message : error);
+  process.exitCode = 1;
+});