The first phase of the ceasefire that paused 15 months of brutal warfare between Israel and Hamas militants is set to end on Saturday. It’s unclear what comes next. The two sides were supposed to start negotiating a second phase weeks ago in which Hamas would release all the remaining hostages from its Oct. 7, 2023, attack in exchange for more Palestinian prisoners, a lasting ceasefire and a full Israeli withdrawal from the Gaza Strip. But those talks have hardly begun, and the first phase has been jolted by one dispute after another.