Make bench tokenizer configs byte-identical to their source models

The encode benches in huggingface/tokenizers load their model configs from this dataset. Some entries were slimmed-down fixtures or diverged from the source models, which made bench numbers unrepresentative (reported as "vocab is smaller than the real model"). This PR makes every bench config byte-identical to `tokenizer.json` in the original model repo:

- `gpt-oss.json` (new): from `openai/gpt-oss-20b` (byte-identical in `openai/gpt-oss-120b`). 199,998 vocab / 446,189 merges vs 3,060 / 4,000 in `gpt-oss-slim.json`.
- `glm-5.2.json` (new): from `zai-org/GLM-5.2`. 154,820 vocab / 321,649 merges vs 2,951 / 4,000 in `glm-5.2-slim.json`.
- `gemma-4.json` (new): from `google/gemma-4-31B-it` (the variant `gemma-4-slim.json` was derived from — vocab/merges are identical across gemma-4 sizes, only the base models' post_processor differs). 262,144 vocab / 514,906 merges vs 2,787 / 4,000 in the slim file.
- `mistral-small-4.json` (new): from `mistralai/Mistral-Small-4-119B-2603` — the current tekken chain (`Sequence[Split, ByteLevel]` pre-tokenizer, 131,072 vocab, 1,000 added special tokens), a workload archetype the benches didn't cover.
- `llama-2.json` (refresh): synced byte-identical with `meta-llama/Llama-2-7b-hf`. The previous copy had the same vocab and merge set but 119 trailing whitespace merges in a different order — merge order is BPE priority, so whitespace runs tokenized differently.
- `llama-3-tokenizer.json` (refresh): synced byte-identical with `meta-llama/Llama-3.1-8B` (the file was already semantically this tokenizer, but re-serialized in the tuple-merges format, 17.2MB vs 9.1MB). Vocab, merges, and added tokens are unchanged — encode ids are identical.
- `.gitattributes`: track the three new configs via LFS/Xet, same as the other full configs.

The `-slim` fixtures are left untouched. The bench manifest in huggingface/tokenizers points at the full configs as of the fix/bpe-benches branch.

.gitattributes

@@ -67,3 +67,7 @@ t5-base.json filter=lfs diff=lfs merge=lfs -text
 llama-2.json filter=lfs diff=lfs merge=lfs -text
 gpt2.json filter=lfs diff=lfs merge=lfs -text
 fixtures/models/** filter=lfs diff=lfs merge=lfs -text
+gpt-oss.json filter=lfs diff=lfs merge=lfs -text
+glm-5.2.json filter=lfs diff=lfs merge=lfs -text
+gemma-4.json filter=lfs diff=lfs merge=lfs -text
+mistral-small-4.json filter=lfs diff=lfs merge=lfs -text

gemma-4.json

@@ -0,0 +1,3 @@
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+size 32169626

glm-5.2.json

@@ -0,0 +1,3 @@
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+size 20217442

gpt-oss.json

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
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+size 27868174

llama-2.json

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
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-size 1842764
+oid sha256:bcd04f0eadf90287bd26e1a183ac487d8a141b09b06aecb7725bbdd343640f2e
+size 1842767

llama-3-tokenizer.json

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:6b9e4e7fb171f92fd137b777cc2714bf87d11576700a1dcd7a399e7bbe39537b
-size 17209920
+oid sha256:76e48799b099d43365bd24ccd8ecc5aedac831718da780552f03b0a6eb4412aa
+size 9085658

mistral-small-4.json

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:2ba5b3330fd84d5376fcca797cfb3b42eee6241ce23e3271e6fb2a115a8751bd
+size 17077420