Conic primitives for the RustUse geometry workspace.
`use-conic` begins with named conic-family value types and lightweight validation. It does not
attempt symbolic equation manipulation or fitting algorithms.
```rust
use use_conic::{ConicKind, Ellipse};
use use_point::Point2;
let ellipse = Ellipse::new(Point2::origin(), 4.0, 2.0).expect("positive radii");
assert_eq!(ellipse.kind(), ConicKind::Ellipse);
assert_eq!(ellipse.major_radius(), 4.0);
```