South Korea’s impeached president, Yoon Suk Yeol, has been arrested and is to undergo questioning over his ill-fated declaration of martial law last month, anti-corruption investigators said on Wednesday, bringing to an end an early-morning standoff outside his official residence in Seoul. Yoon remained defiant, however, saying he had agreed to cooperate with anti-corruption authorities to “avoid bloodshed” after the latest chapter in a saga that has rocked South Korean politics and triggered concern among its allies. Yoon said the rule of law had “completely collapsed” after his detention. “President Yoon has decided to personally appear at the Corruption Investigation