[BUG]: Windows system search does use PATH, contrary to docs #3137

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Type of Bug

Runtime Error

Component

cuda.pathfinder

Describe the bug

The load_nvidia_dynamic_lib docs say that on Windows the system search step doesn't look at PATH. #1781 was closed on that basis. But in practice it does find DLLs on PATH.
We hit this in nvmath-python CI. CUDA_PATH pointed at CTK 12.8, but CTK 13.4 was also on PATH:

load_nvidia_dynamic_lib("cublasLt")
-> ...\CUDA\v13.4\bin\x64\cublasLt64_13.dll, found_via="system-search"

System search runs before the CUDA_PATH step, so the 13.4 DLL won over the toolkit we'd selected. cutensor (cu12 wheel) then failed to load with Windows error 126, because it needs cublasLt64_12.dll.

How to Reproduce

Small repro, no CUDA needed. It makes the same call pathfinder's system search makes
(LoadLibraryExW(name, NULL, 0) in load_with_system_search), with a dummy DLL that
only lives in a folder on PATH:

import ctypes, os, shutil, subprocess, sys, tempfile
d = tempfile.mkdtemp()
shutil.copy(os.path.join(os.environ["SystemRoot"], "System32", "version.dll"),
            os.path.join(d, "zz_probe.dll"))
child = ("import ctypes; k = ctypes.WinDLL('kernel32');"
         "k.LoadLibraryExW.restype = ctypes.c_void_p;"
         "print(bool(k.LoadLibraryExW('zz_probe.dll', None, 0)))")
env = dict(os.environ, PATH=d + os.pathsep + os.environ["PATH"])
subprocess.run([sys.executable, "-c", child], env=env)  # prints True

Expected behavior

load_nvidia_dynamic_lib("cublasLt") should either skip PATH on as doc claimed on windows, or update the docs

Operating System

Windows

nvidia-smi output

No response