fix(ci): supply selected Windows Conda native DLL path

Successful statsmodels workers crash in native SVD/Newton with delayed procedure-load error 0xc06d007f, while the activated coordinator passes. Give test-owned Windows Conda workers only the selected base Python Library/bin plus Execute's default PATH so delayed BLAS dependencies can resolve without inheriting the coordinator environment.

Verification: controlled selected-runtime, absent-directory, POSIX and ambient-PATH exclusion cases pass; fatal lint and whitespace pass. Exact native versions and all worker assertions remain unchanged. Hosted Windows rerun must confirm the native diagnosis.

Author: krafczyk

tests/models/test_estimator_experiments.py

@@ -9,6 +9,7 @@
 import json
 import os
 from pathlib import Path
+import sys
 import tempfile
 
 import numpy as np
@@ -191,6 +192,9 @@ def _executor(tmp_path, repo, control):
     environment.update({name: "1" for name in (
         "OMP_NUM_THREADS", "OPENBLAS_NUM_THREADS", "MKL_NUM_THREADS", "BLIS_NUM_THREADS",
         "NUMEXPR_NUM_THREADS", "VECLIB_MAXIMUM_THREADS")})
+    native_dlls = Path(sys.base_prefix) / "Library" / "bin"
+    if os.name == "nt" and native_dlls.is_dir():
+        environment["PATH"] = os.pathsep.join((str(native_dlls), os.defpath))
     return Executor(SubProcessConfig(
         spool_directory=spool, env_vars=environment, execution_timeout=90,
         automatic_environment_discovery=False, admission_timeout=60,