A prominent doctor who had become a voice for besieged Palestinians in Gaza and was detained by Israeli forces in December has had his detention without charge extended, his family and legal representatives said Thursday. The family and supporters of Dr. Hussam Abu Safiya, the head of Kamal Adwan Hospital in northern Gaza, had hoped he would be released under a ceasefire deal, along with dozens of medical workers who had been detained during Israel’s offensive in the Palestinian enclave.