Add documentation for whole-index distance metrics.

Adds documentation describing metrics that operate directly on kmer sets or counts stored in an index, clarifying that they do not require per-locus SNP calling.

theory-phylogeny-kmer_based-distance_metrics.md

@@ -1,6 +1,6 @@
 # Whole-index distance metrics
 
-These metrics operate on the kmer sets or counts stored in an index directly — no per-locus SNP calling, no sibling annex required. `A`/`B` denote the two genomes being compared; $c_i^A$/$c_i^B$ are their raw counts at kmer $i$, $p_i^A$/$p_i^B$ the corresponding relative frequencies ($p_i = c_i / \sum_j c_j$).
+These metrics operate on the kmer sets or counts stored in an index directly — no per-locus SNP calling, no sibling annex required. `A`/`B` denote the two genomes being compared; $c_i^A$ / $c_i^B$ are their raw counts at kmer $i$, $p_i^A$ / $p_i^B$ the corresponding relative frequencies ($p_i = c_i / \sum_j c_j$).
 
 | Metric | Definition |
 | --- | --- |