The firefighters who rushed to Ground Zero on Sept. 11 of 2001 can still vividly remember the plumes of black smoke clouding that Tuesday morning’s sunny blue skies. Many have spoken about the distinct smell in the air after the World Trade Center towers fell, and the sounds of horrified screams from confounded citizens.  The FDNY lost 343 of the city’s bravest during the attacks, which left permanent physical and emotional scars on hundreds more whose lives, and whose world, changed in an instant.  For the children of those heroic first responders, though, the post-9/11 world is the only life that their adult selves have ever truly known — and the compulsion to run …