e1d59fde54
Introduces a new `merge` CLI subcommand and underlying implementation to consolidate multiple pre-indexed k-mer indexes into a single output. Adds `append_column` methods to persistent bit and int matrices to enable incremental genome column expansion without rebuilding the MPHF. Includes new error variants for index readiness and configuration mismatches, adds a `--force` flag to the index command, and updates documentation and navigation structure accordingly.