合并 Grok SSO 多 flow 重构

吸收 Grok 注册与 webchat2api SSO Cookie 导出流程，并把 Kiro/Grok 验证码轮询统一到共享 flow 邮件轮询服务。保留 master 上 Kiro 页面恢复、active verify-otp 接管和重注入修复，补齐对应测试适配。

background/message-router.js

@@ -17,6 +17,7 @@
       deleteAccountRunHistoryRecords,
       clearAutoRunTimerAlarm,
       clearFreeReusablePhoneActivation,
+      clearGrokSsoCookies,
       clearLuckmailRuntimeState,
       clearYydsMailRuntimeState,
       clearStopRequest,
@@ -1148,6 +1149,13 @@
           return await clearFreeReusablePhoneActivation();
         }
 
+        case 'CLEAR_GROK_SSO_COOKIES': {
+          if (typeof clearGrokSsoCookies !== 'function') {
+            throw new Error('Grok SSO 清空能力未接入。');
+          }
+          return await clearGrokSsoCookies();
+        }
+
         case 'SET_FREE_REUSABLE_PHONE': {
           if (typeof setFreeReusablePhoneActivation !== 'function') {
             throw new Error('白嫖复用手机号记录能力未接入。');