fix(auth): defer guest login until chat entry

src/stores/auth/auth-context.tsx

@@ -58,7 +58,7 @@ export function AuthProvider({ children }: AuthProviderProps) {
       username: state.context.username,
       confirmPassword: state.context.confirmPassword,
       // isLoading 覆盖邮箱登录 / 邮箱注册 / OAuth 跳转（NextAuth 重定向期间）/
-      // OAuth 回调后端 sync / 自动游客登录
+      // OAuth 回调后端 sync / 显式游客登录
       isLoading:
         state.matches("loadingEmailLogin") ||
         state.matches("loadingEmailRegister") ||