feat(exports): export datagram handler types and align tests with updated nftables and route security APIs

test/test.route-security.ts

@@ -148,7 +148,8 @@ tap.test('route-specific IP block list should be enforced', async () => {
       try {
         client.write('test data');
       } catch (e) {
-        console.log('Write failed:', e.message);
+        const message = e instanceof Error ? e.message : String(e);
+        console.log('Write failed:', message);
       }
     });
     
@@ -272,4 +273,4 @@ tap.test('routes without security should allow all connections', async () => {
   });
 });
 
-export default tap.start();
+export default tap.start();