Function rolling_mean_int_to 

pub fn rolling_mean_int_to<T: NumCast + Copy + Zero>(
    data: &[T],
    mask: Option<&Bitmask>,
    subwindow: usize,
    out: &mut [f64],
    out_mask: &mut Bitmask,
)

Zero-allocation variant that writes directly to caller-provided output buffers.