WASHINGTON — Charlie Kirk’s alleged shooter Tyler Robinson was living with a transgender partner who was in the process of transitioning from a male to a female, a law enforcement source confirmed to The Post Saturday. That individual, who has yet to be identified by the authorities, is now fully cooperating with the FBI on its investigation into the fatal shooting of the conservative activist, the source added. The relationship was first reported by Fox News’ Brooke Singman. Text messages and other communications that the transgender individual traded with Robinson, 22, helped the feds nab the accused assassin. Federal and...