fix: add error handling for server startup failures (#236)

Previously, if app.listen() failed (e.g., port already in use), the
server would fail silently. This adds proper error handling to log
the error and exit with a non-zero status code.

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

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

examples/basic-server-react/server-utils.ts

@@ -54,7 +54,11 @@ export async function startServer(
     }
   });
 
-  const httpServer = app.listen(port, () => {
+  const httpServer = app.listen(port, (err) => {
+    if (err) {
+      console.error("Failed to start server:", err);
+      process.exit(1);
+    }
     console.log(`${name} listening on http://localhost:${port}/mcp`);
   });