Function minimum_node_cut 

pub fn minimum_node_cut(
    graph: &Graph,
    source: &str,
    sink: &str,
) -> MinimumNodeCutResult

Compute minimum s-t node cut: the smallest set of nodes whose removal disconnects s from t.

Uses node-splitting + Edmonds-Karp, then BFS on residual to find min-cut nodes. Matches networkx.algorithms.connectivity.minimum_node_cut(G, s, t).