Function jitter_unit 

pub fn jitter_unit() -> f64

A value in [0.0, 1.0) for use as jitter_unit.

The bar here is “decorrelates concurrent clients”, not statistical uniformity: two processes would have to back off within the same nanosecond to collide. That is met without a dependency, which matters because the workspace already carries several rand versions and neither consumer of this needs a third.

decide clamps whatever it receives, so a coarse clock on some platform can degrade the spread but cannot produce an invalid delay.