fix(signin): align check-in feedback with reference theme

tests/widget-system/captcha-runtime-harness.test.cjs

@@ -115,11 +115,13 @@ test('sign-in waits for main before binding and invokes the signin captcha', asy
   const button = {
     dataset: {},
     disabled: false,
+    attrs: {},
     classList: { toggle() {} },
+    setAttribute(name, value) { this.attrs[name] = value; },
+    removeAttribute(name) { delete this.attrs[name]; },
     addEventListener(name, handler) { listeners[name] = handler; },
     querySelector(selector) { return selector === '[data-signin-label]' ? label : null; },
     getAttribute(name) {
-      if (name === 'data-signin-idle-label') return '签到';
       if (name === 'data-signin-done-label') return '已签到';
       return '';
     },