Add CodonTranslator dataset card and license

LICENSE

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+This dataset release is provided under the Creative Commons Attribution 4.0
+International license (CC-BY-4.0).
+
+https://creativecommons.org/licenses/by/4.0/

README.md

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+---
+license: cc-by-4.0
+pretty_name: CodonTranslator Data
+task_categories:
+  - text-generation
+tags:
+  - biology
+  - dna
+  - codon-optimization
+  - protein-conditioned-generation
+size_categories:
+  - 10M<n<100M
+---
+
+# CodonTranslator Data
+
+This repository contains the final public training-data release used for CodonTranslator.
+
+## Contents
+
+- `train/`: representative-only training shards
+- `val/`: representative-only validation shards
+- `test/`: representative-only held-out test shards
+- `embeddings_v2/`: precomputed species conditioning embeddings used in training
+- `_work/final_representative_counts.json`: final released split sizes
+- `_work/split_report.json`: split audit report
+- `_work/cluster_split.parquet`: cluster-level split assignments
+- `_work/seq_cluster.parquet`: MMseqs cluster assignments
+- `_work/seq_split.parquet`: split assignments before representative selection
+
+## Split definition
+
+The public `data_v3` split was rebuilt from `data_v2` with the following rules:
+
+- MMseqs clustering in **protein space**
+- test holdout by **binomial species**
+- validation split from **seen species but unseen clusters**
+- representative-only parquet outputs, one retained row per released representative sequence
+
+Mixed seen/held-out protein clusters and exact-protein leakage cases are removed on the seen side before final release.
+
+## Final released split sizes
+
+- `train = 36,888,301`
+- `val = 373,637`
+- `test = 331,455`
+
+All three released splits satisfy:
+
+- exact protein overlap `train/val = 0`
+- exact protein overlap `train/test = 0`
+- test species not seen in train/val
+- representatives-only rows, so `rows == unique_seq_id`
+
+## Parquet schema
+
+Each released parquet shard contains these columns:
+
+- `RefseqID`
+- `protein_refseq_id`
+- `protein_seq`
+- `cds_DNA`
+- `taxon`
+- `shard`
+
+## Embeddings
+
+`embeddings_v2/` is the exact species embedding store used in training. It contains:
+
+- `species_vocab.json`
+- `species_index.json`
+- `species_tok_emb.bin`
+- `metadata.json`
+- `taxonomy_database.json`
+
+The released `data_v3` taxa are fully covered by this embedding store.
+
+## Model and code
+
+The corresponding public model and code release is:
+
+- `alegendaryfish/CodonTranslator`
+
+## Attribution
+
+This release redistributes processed training data and derived embeddings for reproducibility of the CodonTranslator experiments. See the audit files in `_work/` for construction details and final verification outputs.