WASHINGTON — A US government watchdog has found at least four more staffers for the United Nations’ Palestinian refugee aid agency “kidnapped” Israelis and aided Hamas’ terror attack on Oct. 7, 2023, information that is likely to feed into a federal criminal probe, sources told The Post. The USAID Office of Inspector General, in an April 30 investigative summary, cited “four additional current or former staff” at the UN Relief and Works Agency for Palestine Refugees, three of whom were teachers