Function render_and_encode 

pub(crate) fn render_and_encode(
    image: Rgb32FImage,
    preset: Option<&Preset>,
    output_path: &Path,
    metadata: Option<&ImageMetadata>,
    use_gpu: bool,
) -> Result<()>

Render a decoded image with an optional preset and encode to PNG. Used by run_multi_apply for both sequential and parallel paths.