Function exact_plane_analytic 

pub fn exact_plane_analytic(
    surface: AnalyticSurface<'_>,
    plane_normal: Vec3,
    plane_d: f64,
) -> Result<Vec<ExactIntersectionCurve>, MathError>

Compute exact intersection curves between a plane and an analytic surface.

Returns exact Circle3D or Ellipse3D where possible, falling back to sampled points for complex cases (torus).

The plane is defined by dot(normal, p) = d.

Errors

Returns an error if the intersection computation fails.