Function validate_frontier_queue_query 

pub fn validate_frontier_queue_query(
    node_count: u32,
    frontier: &[u32],
    queue_capacity: u32,
) -> Result<usize, String>

Validate one packed frontier for queue-driven CSR traversal.

Returns the exact packed frontier word count implied by node_count, so a resident dispatch wrapper can size scratch without duplicating queue and frontier-shape policy.

Errors

Returns an actionable diagnostic for zero-node graphs, zero queue capacity, or a frontier whose packed bitset width does not match node_count.