edd5e3f8ee
Introduce a `stats` module to compute normalized storage efficiency metrics. The new `KmerIndex::bits_per_kmer()` method parallelizes disk I/O across partitions to aggregate file sizes for MPHF, evidence, and matrix components. Publicly export `IndexBitsPerKmer` and add a `--bits-per-kmer` CLI flag to trigger the diagnostic routine and print detailed statistics.