Function apply_layer_adjoint 

pub fn apply_layer_adjoint<const W: usize, C, T>(
    input: &PauliSum<W>,
    channel: &C,
    policy: &T,
) -> PauliSum<W>
where
    C: Channel<W> + ?Sized,
    T: TruncationPolicy<W> + ?Sized,

Apply a channel’s adjoint to a PauliSum. Used by propagate in Direction::Heisenberg mode; structurally identical to apply_layer but routes through Channel::apply_adjoint.