Function ifds_node_count 

pub fn ifds_node_count(
    num_procs: u32,
    blocks_per_proc: u32,
    facts_per_proc: u32,
) -> u32

Total node count of the exploded supergraph for the given dimensions. Equivalent to row_ptr.len() - 1 after the CSR is built; useful when the caller needs to size frontier bitsets before invoking build_ifds_csr.