With his grasp on power slipping, Japan’s Prime Minister Shigeru Ishiba has vowed to remain in office despite a stinging electoral rebuke that plunged his ruling coalition into fresh turmoil.The humiliating setback, confirmed late on Sunday, has fuelled doubts about Ishiba’s leadership as rivals within his Liberal Democratic Party (LDP) circle and stoked anxiety in the world’s fourth-largest economy, already reeling from rising prices, mounting security threats and the disruptive effects of US...