Add README (repo layout) and xet/LFS rule for fixtures/

.gitattributes

@@ -60,3 +60,4 @@ saved_model/**/* filter=lfs diff=lfs merge=lfs -text
 *.webm filter=lfs diff=lfs merge=lfs -text
 llama-3-tokenizer.json filter=lfs diff=lfs merge=lfs -text
 xnli.txt filter=lfs diff=lfs merge=lfs -text
+fixtures/**/*.txt filter=lfs diff=lfs merge=lfs -text

README.md

@@ -0,0 +1,36 @@
+---
+pretty_name: tokenizers test data
+viewer: false
+---
+
+# tokenizers-test-data
+
+Test and benchmark fixtures for [huggingface/tokenizers](https://github.com/huggingface/tokenizers),
+pulled on demand by the repo Makefiles (`make test` / `make bench` / `make fixtures`
+via `hf download`).
+
+## Layout
+
+- `fixtures/` — multilingual + modality corpora for cross-language encode
+  benchmarks. Organized, documented, and reproducible: see
+  [`fixtures/FIXTURES.md`](./fixtures/FIXTURES.md) for provenance and
+  [`fixtures/fixtures_manifest.json`](./fixtures/fixtures_manifest.json) for
+  exact sources, pinned revisions, and sizes. Rebuild any file with
+  [`fixtures/fetch_fixtures.py`](./fixtures/fetch_fixtures.py).
+  - `fixtures/lang/<iso639-3>_<iso15924>.txt` — ~5 MB of real web text per
+    language (FineWeb-2 / FineWeb), 13 non-Latin scripts + English baseline
+  - `fixtures/modalities/` — source code, math/LaTeX, and coding-agent
+    trajectories
+- **Root files (legacy)** — tokenizer JSONs, vocab/merges files, and text
+  corpora referenced by their flat paths from the `tokenizers` repo Makefiles
+  (Rust, Python, and Node bindings) on `main` and release branches. Do not
+  move or rename them; new additions should go into organized subdirectories
+  instead.
+
+## Licensing
+
+Corpora under `fixtures/` are small excerpts of public datasets, each under
+its own license — FineWeb/FineWeb-2 (ODC-By), open-web-math (ODC-By),
+SWE-smith-trajectories (MIT), and permissively-licensed OSS repos for code
+(see the manifest for the exact repo list and commit SHAs). Root-level files
+predate this README and carry the licenses of their original sources.