test(js): cover confirm dispatch guard

Cover data-slhx-confirm as a runtime convention boundary: confirmation happens before handler dispatch continues.

req: convention/004

slhx-js/tests/runtime.rs

@@ -9,6 +9,15 @@ fn runtime_posts_urlencoded_forms_by_default() {
     assert!(source.contains("application/x-www-form-urlencoded;charset=UTF-8"));
 }
 
+#[test]
+fn runtime_confirms_before_handler_dispatch() {
+    // req: convention/004
+    let source = slhx_js::RUNTIME_JS;
+
+    assert!(source.contains("el.getAttribute(\"data-slhx-confirm\") && !confirm(el.getAttribute(\"data-slhx-confirm\"))"));
+    assert!(source.contains("return;"));
+}
+
 #[test]
 fn runtime_fetches_with_same_origin_credentials() {
     // req: auth/005