fix: explicitly handle special case in circular segment area

[severinstrobl]

No description provided.

[overlap-benchmarks]

C++ benchmark results

Benchmark	Reference (3d30bc4)	Current (f39db6e)
tet_overlap_volume[sphere-in-hex]	1.33 us	1.33 us: 1.00x slower
Geometric mean	(ref)	1.00x slower

Benchmark hidden because not significant (8): hex_overlap_volume[AABB], hex_overlap_volume[hex-in-sphere], hex_overlap_volume[random], hex_overlap_volume[sphere-in-hex], normal_newell, regularized_wedge, tet_overlap_volume[AABB], tet_overlap_volume[hex-in-sphere]

Python benchmark results

Benchmark	Reference	Current
hex_overlap_volume[random]	9.95 us	9.87 us: 1.01x faster
hex_overlap_volume[sphere-in-hex]	2.29 us	2.27 us: 1.01x faster
tet_overlap_volume[sphere-in-tet]	1.16 us	1.15 us: 1.00x faster
tet_overlap_volume[tet-in-sphere]	297 ns	323 ns: 1.09x slower
tet_overlap_volume[AABB]	285 ns	305 ns: 1.07x slower
Geometric mean	(ref)	1.02x slower

Benchmark hidden because not significant (2): hex_overlap_volume[hex-in-sphere], hex_overlap_volume[AABB]