Document workaround for numpy lazy loading issue

Add comments to explain pre-importing numpy's lazy submodules to avoid CPython issue.

Author: SwayamInSync

tests/conftest.py

@@ -1,3 +1,9 @@
+# Pre-import numpy's lazy submodules in single-threaded context before
+# pytest-run-parallel forks workers. Works around CPython issue https://github.com/python/cpython/issues/149728 
+# which causes numpy's lazy __getattr__ on rec/ma/linalg/fft/... to recurse
+# to RecursionError under concurrent first-touch from multiple threads.
+# Drop this file when CPython bugfix release happens.
+
 import numpy
 
 for _attr in (