[BUG] HSLColor always renders as solid red, ignoring hue adjustments

[goodguyjay]

Describe the bug

Drawing with HSLColor(hue, 1.0, 0.5) produces a solid red image regardless of hue.
Expected behaviour: hue 0 -> red, 120 -> green, 240 -> blue (smooth gradient).

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Environment

Item	Value
Plotters version	0.3.7
Rust version	1.86.0
OS / Toolchain	Windows 11

I'm pulling from cargo.

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To Reproduce

use plotters::prelude::*;
use plotters::style::HSLColor;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let root = BitMapBackend::new("hsl_test_output.png", (200, 200)).into_drawing_area();
    root.fill(&WHITE)?;

    // sweep hue 0° (red) -> 240° (blue) horizontally
    for x in 0..200 {
        let hue = 240.0 * x as f64 / 200.0;
        let color = HSLColor(hue, 1.0, 0.5);
        for y in 0..200 {
            root.draw_pixel((x as i32, y as i32), &color)?;
        }
    }

    root.present()?;
    Ok(())
}

Actual output:

Expected output

The same sweep converted manually HSL -> RGB shows the full spectrum:

import numpy as np, matplotlib.pyplot as plt, colorsys, imageio.v3 as iio

w = 200
img = np.zeros((w, w, 3), dtype=np.uint8)
for x in range(w):
    hue = 240.0 * x / w / 360.0          # hue in [0,1]
    r, g, b = colorsys.hls_to_rgb(hue, 0.5, 1.0)
    img[:, x] = (np.array([r, g, b]) * 255).astype(np.uint8)

iio.imwrite("expected_hsl_gradient.png", img)

[zxq82lm]

I opened a PR to fix this: #703.