Incorrect dependency constraint on compressed-tensors leads to ImportError (is_fp4)

[butterShoter]

'llm-compressor' currently declares the following dependency:

# ./workspace/llm-compressor/setup.py, line 143
(
            "compressed-tensors==0.12.1"
            if BUILD_TYPE == "release"
            else "compressed-tensors>=0.12.2a2"
 ),

However, the code imports an internal API that is not stable across versions:

from compressed_tensors.quantization.utils import is_fp4

With a clean environment, this this can result in installation of newer alpha versions
(e.g. compressed-tensors==0.13.1.a*), where is_fp4 is no longer available
(or not exported), leading to an immediate ImportError at import time.

Reproduction

1. Create a clean environment
2. pip install -e . (or uv pip install -e .)
3. import llmcompressor
   This installs compressed-tensors==0.13.x and fails with:
   ImportError: cannot import name 'is_fp4'

Expected Behavior

The dependency should be pinned or constrained to versions that are known
to expose the required API, e.g.:
compressed-tensors==0.12.2a2 or compressed-tensors>=0.12.2a2,<0.13

Notes

Since this relies on an internal (non-public) API, a strict pin or upper bound
seems necessary to ensure reproducibility.