Fix title underline and test pathfinder documentation build

Co-authored-by: leofang <5534781+leofang@users.noreply.github.com>

Author: Copilot

cuda_pathfinder/docs/source/index.rst

@@ -2,7 +2,7 @@
 .. SPDX-License-Identifier: Apache-2.0
 
 ``cuda.pathfinder``: Utilities for locating CUDA components
-=========================================================
+===========================================================
 
 .. include:: ../../cuda/pathfinder/README.md
    :parser: myst_parser.sphinx_