[CI] Install sgl-eval from PyPI through the test extra (#37504)

python/pyproject.toml

@@ -172,11 +172,8 @@ test = [
   "lm-eval[api]>=0.4.9.2",
   "matplotlib",
   # 4.9.3 is what sgl-eval's math_verify grader needs (latex2sympy2_extended
-  # raises ImportError on 4.7.x), so a `sglang[test]` environment is already
-  # compatible when sgl-eval is installed on top of it.
-  # Do NOT declare sgl-eval itself here: it is git-only, and PyPI rejects any
-  # uploaded distribution whose metadata carries a direct URL requirement.
-  # CUDA CI installs it in scripts/ci/cuda/ci_install_dependency.sh.
+  # raises ImportError on 4.7.x); pinned here so other test deps cannot pull
+  # it down.
   "antlr4-python3-runtime==4.9.3",
   "pandas",
   "parameterized",
@@ -185,6 +182,10 @@ test = [
   "pytest",
   "pytest-cov",
   "sentence_transformers",
+  # Pinned: a bump moves scoring for every eval test at once, so re-baseline
+  # MODEL_SCORE_THRESHOLDS in test/registered/eval/test_text_models_gsm8k_eval.py
+  # and the mmlu thresholds of run_eval's other callers before changing it.
+  "sgl-eval==0.1.0",
   "sglang[fastokens]",
   "tabulate",
 ]