fix: restart phone signup when password page rejects number

- 合并 PR #214 的核心改动：将密码页手机号已关联账号/phone already exists 归为可重开的注册手机号异常，并补充回归覆盖。
- 本地补充修复：无。
- 影响范围：content/signup-page.js 的 Step 3/4 注册验证码前置检查、step4 split-code 测试。

content/signup-page.js

@@ -2493,7 +2493,7 @@ const SIGNUP_PHONE_PASSWORD_MISMATCH_ERROR_PREFIX = 'SIGNUP_PHONE_PASSWORD_MISMA
 const AUTH_MAX_CHECK_ATTEMPTS_ERROR_PREFIX = 'AUTH_MAX_CHECK_ATTEMPTS::';
 const STEP8_EMAIL_IN_USE_ERROR_PREFIX = 'STEP8_EMAIL_IN_USE::';
 const SIGNUP_EMAIL_EXISTS_PATTERN = /与此电子邮件地址相关联的帐户已存在|account\s+associated\s+with\s+this\s+email\s+address\s+already\s+exists|email\s+address.*already\s+exists/i;
-const SIGNUP_PHONE_PASSWORD_MISMATCH_PATTERN = /incorrect\s+phone\s+number\s+or\s+password|phone\s+number\s+or\s+password/i;
+const SIGNUP_PHONE_PASSWORD_MISMATCH_PATTERN = /incorrect\s+phone\s+number\s+or\s+password|phone\s+number\s+or\s+password|与此(?:电话|手机)号码相关联的帐户已存在|account\s+associated\s+with\s+this\s+phone\s+number\s+already\s+exists/i;
 
 const authPageRecovery = self.MultiPageAuthPageRecovery?.createAuthPageRecovery?.({
   detailPattern: AUTH_TIMEOUT_ERROR_DETAIL_PATTERN,
@@ -2552,9 +2552,9 @@ function createSignupUserAlreadyExistsError() {
 
 function createSignupPhonePasswordMismatchError(detailText = '') {
   const detail = String(detailText || '').replace(/\s+/g, ' ').trim();
-  const suffix = detail ? `页面提示：${detail}` : '页面提示手机号或密码不正确。';
+  const suffix = detail ? `页面提示：${detail}` : '页面提示注册手机号不可继续使用，需重新开始当前轮。';
   return new Error(
-    `${SIGNUP_PHONE_PASSWORD_MISMATCH_ERROR_PREFIX}步骤 3：检测到注册手机号或密码不正确，需要重新开始当前轮。${suffix}`
+    `${SIGNUP_PHONE_PASSWORD_MISMATCH_ERROR_PREFIX}步骤 3：检测到注册手机号异常，需要重新开始当前轮。${suffix}`
   );
 }