Will its tale be primarily one of pain, focused on America’s history of slavery and racial oppression, and memorializing black suffering? Or will it emphasize the uplifting part of the story, highlighting the richness of African-American culture, celebrating the bravery of civil rights heroes and documenting black “firsts” in fields like music, art, science and sports? Will the story end with the country’s having overcome its shameful history and approaching a state of racial harmony and equality? Or will the museum argue that the legacy of racism is still dominant — and, if so, how will it make that case?