Reweighting
Reweighting is the step that turns reusable support into a target-k graph.
get_core_sg_mutual_reachability_distance(k) returns the support graph with
mutual-reachability weights for a valid k:
weighted = core.get_core_sg_mutual_reachability_distance(k=10)
The implementation reuses support_graph_, metric_edges_, and
core_distances_. It does not rebuild the original neighbor graph for each
target k.