Add regression test for non-overlapping polygon intersection (issue #1439)

[kashish2710]

This PR adds a minimal regression test reproducing issue #1439.

The test shows that boost::geometry::intersection currently produces a non-empty result for two polygons that do not overlap.

The test fails on Boost 1.89 (tested on Linux / Google Colab), confirming that the reported behavior is still present.

Once the underlying issue is fixed, this test will help ensure that the behavior does not regress in future changes.

Still reproducible on Boost 1.89 (Linux). See attached output showing non-empty intersection for non-overlapping polygons.