Function insphere_filter 

pub fn insphere_filter(
    a: Point3,
    b: Point3,
    c: Point3,
    d: Point3,
    e: Point3,
) -> Certified

The fast filter alone, exposed so escalation can be measured.

Returns Certified::Uncertain when a nonzero coordinate difference is outside [2^-128, 2^128), where a product may overflow or underflow.