add name-tree command and fix --free-loss cost matrix

Introduce the obikmer name-tree subcommand to map numeric leaf labels in phylogenetic tree exports back to taxon names using a reference FASTA file. Correct the --free-loss flag behavior by removing cardinality transition costs from pairwise cost calculations, ensuring sibling gains and losses are priced identically to whole-family events. Update documentation, configuration parameters, and add reference phylogenetic data files.

UserDocMD/index.md

@@ -25,6 +25,7 @@ All functionality is exposed through a single binary, `obikmer`, organized as su
 | [`dump`](usage/dump.md) | Dump indexed kmers as CSV |
 | [`annotate`](usage/annotate.md) | Add, update, or dump genome metadata |
 | [`phylo`](usage/phylo.md) | Compute pairwise evolutionary-distance proxies, trees, and phylogenetic exports |
+| [`name-tree`](usage/name-tree.md) | Translate a TNT/PhyG numeric-label tree export back to real taxon names |
 | [`unitig`](usage/unitig.md) | Dump the unitigs of an index as FASTA |
 | [`estimate`](usage/estimate.md) | Estimate approximate-index parameters before indexing |
 | [`reindex`](usage/reindex.md) | Convert an index's evidence representation (exact ↔ approximate) |

UserDocMD/usage/name-tree.md

@@ -0,0 +1,21 @@
+# name-tree
+
+Translate a numerically-labelled tree export (TNT, PhyG, or any plain Newick file with bare `1`, `2`, `3`, … leaf labels) back to real taxon names, reading the label order from the FASTA that produced it.
+
+```bash
+obikmer name-tree TREE --fasta FASTA -o OUTPUT
+```
+
+## Arguments
+
+| Argument | Description |
+|---|---|
+| `TREE` | Tree file to translate — a TNT-style NEXUS export (`tree NAME = [&U] ...;`) or a plain Newick file |
+| `--fasta` | FASTA file whose record order gives the numeric taxon labels (1-based) — typically the `_sankoff.fasta`/`_snp.fasta` used to produce `TREE` |
+| `-o, --output` | Output NEXUS file path |
+
+## Output
+
+A NEXUS file with a `taxa` block, a `translate` table (numeric label → taxon name, from `--fasta`'s header order), and every tree found in `TREE`, topology unchanged — readable directly in FigTree, PearTree, `ape` (R), etc.
+
+`--tnt`'s and `--phyg`'s exports (see [phylo](phylo.md)) both number taxa `1..N` in the same order as the pseudo-alignment FASTA they were built from (`<prefix>_sankoff.fasta`), so pass that same file as `--fasta` here.

UserDocMD/usage/phylo.md

@@ -93,7 +93,7 @@ which are combined into a row-normalized $16 \times 16$ transition probability m
 
 `--sankoff` alone writes the cost matrix, the calibration parameters, and a pseudo-alignment recoded so the empty state uses the symbol `0` (never a gap character, to avoid ambiguity with external tools' own gap semantics). It does not run any external tool.
 
-With `--free-loss`, the empty state is recoded to `?` instead — TNT/PhyG/IQ-TREE's own missing-data symbol — rather than an ordinary, costed 16th state. This matters for genome-skim or otherwise incomplete-coverage collections, where non-detection of a family is dominated by sampling failure rather than true evolutionary loss: scoring it as a real state risks grouping genomes by shared undersampling instead of shared ancestry. `?` rather than `-` because `-` still carries gap/indel semantics in these tools, and a non-detected family is not an observed deletion. Combine with `--min-shared-family`/`--family-overlap` above: `--free-loss` removes the false signal from non-detection, but a genome left with too little real overlap with everything else will still be placed unstably — excluding it is the other half of the fix.
+With `--free-loss`, the empty state is recoded to `?` instead — TNT/PhyG/IQ-TREE's own missing-data symbol — rather than an ordinary, costed 16th state. This matters for genome-skim or otherwise incomplete-coverage collections, where non-detection of a family is dominated by sampling failure rather than true evolutionary loss: scoring it as a real state risks grouping genomes by shared undersampling instead of shared ancestry. `?` rather than `-` because `-` still carries gap/indel semantics in these tools, and a non-detected family is not an observed deletion. `--free-loss` also drops the cardinality-transition cost between any two states, not just to/from the empty one: whether a genome shows 1 vs. 2 (etc.) detected members of a family it does carry is exactly as vulnerable to sampling failure as whether the family was detected at all, so gaining or losing a sibling is priced the same way — for free — as gaining or losing the whole family. Combine with `--min-shared-family`/`--family-overlap` above: `--free-loss` removes the false signal from non-detection, but a genome left with too little real overlap with everything else will still be placed unstably — excluding it is the other half of the fix.
 
 ### Exports
 
@@ -103,6 +103,8 @@ All three exports reuse the `--sankoff` calibrated matrix and pseudo-alignment,
 - **`--phyg`**: a custom cost-matrix file plus a PhyG script reusing the `--sankoff` alignment directly.
 - **`--iqtree`**: a custom substitution-model file (exchangeability matrix recovered as $R(a,b) = e^{-\text{cost}(a,b)}$, plus empirical state frequencies) and a matching alignment, for maximum-likelihood inference with real branch lengths (unlike the parsimony step-counts from TNT/PhyG). Only states actually occurring in the alignment are kept and compactly renumbered.
 
+TNT and PhyG both write trees with bare numeric leaf labels (`1`, `2`, …, in the same order as `<prefix>_sankoff.fasta`). Use [`name-tree`](name-tree.md) on the tool's own tree output plus that same FASTA to get a NEXUS file with real taxon names.
+
 ## Output files
 
 With `-o/--output PREFIX`, the relevant subset of the following files is written: `<prefix>_dist.csv`, `<prefix>_shared.csv`, `<prefix>_nj.nwk`, `<prefix>_upgma.nwk`, `<prefix>_siblings.csv`, `<prefix>_rawsnp.csv`, `<prefix>_rawsnp_counts.csv`, `<prefix>_snp.fasta`, `<prefix>_family_overlap.csv`, `<prefix>_sankoff_matrix.csv`, `<prefix>_sankoff_params.yaml`, `<prefix>_sankoff.fasta`, `<prefix>_sankoff.tnt`, `<prefix>_sankoff.tcm`, `<prefix>_sankoff.pg`, `<prefix>_iqtree.model`, `<prefix>_iqtree.fasta`. Without `-o`, only the plain `--metric` distance matrix is produced, on stdout.