In a Republican county known as a cradle of border enforcement zeal, Costa Mesa has long been celebrated — and maligned — as a city that offered immigrants a generous embrace. SNIP Last year, the city shut down the dayworker center after 17 years. It abolished its human relations committee after 18 years. And as the city now moves to train local police in immigration enforcement — the nation's first municipality to do so — it has become a flashpoint in a national debate. Outsiders have rushed in, hailing or condemning the city's efforts. There are demonstrations at City Hall,...