Function gpu_bfs_paged 

pub async fn gpu_bfs_paged(
    device: &GpuDevice,
    graph: &CsrGraph,
    source: NodeId,
) -> Result<GpuBfsResult>

Run GPU breadth-first search over a graph that may exceed VRAM.

When the graph fits in GPU memory this delegates to the in-VRAM super::gpu_bfs; otherwise it tiles the graph via PagingCoordinator and processes each tile in turn.

Errors

Returns an error if GPU paging setup or any tile traversal fails.