Function collect_routed_paths

pub fn collect_routed_paths(
    selection: &Selection,
    slice: &Slice,
) -> RoutedPathTree

Simulates routing from the origin through a slice using a Selection, collecting all delivery destinations along with their routing paths. Each returned entry is a tuple (dst, path), where dst is the flat index of a delivery node, and path is the list of flat indices representing the route taken from the origin to that node. Routing begins at [0, 0, ..., 0] and proceeds dimension-by-dimension. At each hop, next_steps determines the next set of forwarding frames. A node is considered a delivery target if:

• its selection is Selection::True, and
• it is at the final dimension. Useful in tests for verifying full routing paths and ensuring correctness.