Description

The library panics with an assertion failure when the radius parameter exceeds sqrt(2)/2 ≈ 0.707:

thread 'Compute Task Pool (4)' panicked at poisson/src/lib.rs:135:9:
assertion failed: radius <= NumCast::from(2f64.sqrt() / 2.).expect("Casting constant should always work.")

Expected Behavior

The library should handle this gracefully, either by:

1. Clamping the radius to the maximum allowed value
2. Returning an error through a Result type
3. Documenting the constraint clearly in the Builder API

Current Behavior

The library uses an assertion that panics at runtime, which is not a graceful failure mode for what appears to be a mathematical constraint rather than a true invariant violation.

Reproduction

use poisson::{Builder, Type, algorithm::Ebeida};
use nalgebra::Vector2;

let radius = 0.8; // Exceeds sqrt(2)/2
let poisson = Builder::<_, Vector2<f32>>::with_radius(radius, Type::Normal);
let generator = poisson.build(rand::thread_rng(), Ebeida);
let points = generator.generate(); // Panics here

Context

This issue was encountered in townmaker when bounding boxes were too small relative to the density setting, causing the normalized radius calculation to exceed the limit.