PHILADELPHIA — Nine Democrats are vying to replace Philadelphia Mayor Jim Kenney, and nearly all of them have said they will do one thing he would not: Declare gun violence a citywide emergency. But it remains to be seen what such a declaration would do. Federal and state officials have long declared states of emergency to unlock new funding and mobilize response teams following natural disasters or civil unrest. But in Philadelphia, emergency declarations at the local level do not automatically lead to new dollars or personnel. That means the impact of such a declaration would largely be defi…