[Transformers v5] Base model and LoRA used in test has incorrect `tokenizer_config.json`

This is a sub-issue forming part of the work in https://github.com/vllm-project/vllm/issues/38379, please read the description of this issue before beginning to work on this one.

Which test is failing?

The tokenizer_config.json is incorrect for both the base model and the adapter. If we duplicated these checkpoints and stored them inside https://huggingface.co/vllm-project, then we could own them and update the tokenizer class to be PreTrainedTokenizerFast which will almost always work.

$ pytest tests/lora/test_quant_model.py::test_quant_model_lora[model0]
...
AssertionError: assert ['#f07733: A ...#f08800: A v'] == ['#f07700: A ...#f00000: A v']
[2026-03-27T01:15:06Z]
[2026-03-27T01:15:06Z]   At index 0 diff: '#f07733: A v' != '#f07700: A v'
[2026-03-27T01:15:06Z]
[2026-03-27T01:15:06Z]   Full diff:
[2026-03-27T01:15:06Z]     [
[2026-03-27T01:15:06Z]   -     '#f07700: A v',
[2026-03-27T01:15:06Z]   ?           ^^
[2026-03-27T01:15:06Z]   +     '#f07733: A v',
[2026-03-27T01:15:06Z]   ?           ^^
[2026-03-27T01:15:06Z]   -     '#f00000: A v',
[2026-03-27T01:15:06Z]   ?         ^^
[2026-03-27T01:15:06Z]   +     '#f08800: A v',
[2026-03-27T01:15:06Z]   ?         ^^
[2026-03-27T01:15:06Z]     ]

How to configure my environment?

It's very important that you install both vLLM and Transformers from source so that your test results reflect the current state of both libraries.

# Or your fork
git clone https://github.com/huggingface/transformers.git
git clone https://github.com/vllm-project/vllm.git

cd vllm
VLLM_USE_PRECOMPILED=1 uv pip install -e .
uv pip install -e ../transformers