BALTIMORE — Imani Holt was just 10 when she saw a neighbor get fatally shot by a triggerman riding a bicycle. The African-American girl from a gritty section of Baltimore was so traumatized by the drug-fueled bloodshed she refused to leave her family’s apartment for weeks. In the eight years since, Holt has seen the chaotic aftermath of two more deadly shootings and has lost seven high school classmates to the daily drip of gun violence. Like many black teenagers in neighborhoods hobbled by generational poverty, she is scrutinizing the national gun control debate intensely, frustrated because her community feels ignored but also cautiously hopeful that the massacre in Florida may bring about change closer to home. “I feel really bad that they lost those kids in Florida.