Joint analysis of paired scRNA-seq and scATAC-seq (10x Multiome) data. Input: --rna <rna.h5ad> --atac <atac.h5ad> [--fragments <fragments.tsv.gz>] --output <dir>. Output: multiome.h5ad, joint_umap.png, peak_gene_links.csv. Note: Stub if sc-multiome not present in OmicsClaw; functional placeholder.