Function read_data_on_shared_rows 

pub fn read_data_on_shared_rows(
    args: ReadSharedRowsArgs,
) -> Result<SparseDataWithBatch>

Load multiple sparse data files, verify shared row names, and auto-detect batch.

Batch assignment priority:

1. Explicit batch files (one label per cell per file)
2. Embedded @-separated batch info in column names (e.g., barcode@donor)
3. File name as batch label (one batch per input file)