BUG: "Unexpected number of edges" occurs with triangles sharing an edge

[dhermes]

The exact representations of the (linear) triangles are:

import numpy as np

nodes1 = np.asfortranarray([
    [
        float.fromhex("-0x1.8000000000000p-1"),
        float.fromhex("-0x1.9555555555556p-1"),
        float.fromhex("-0x1.8000000000000p-1"),
    ],
    [
        float.fromhex("0x1.0000000000000p+0"),
        float.fromhex("0x1.eaaaaaaaaaaaap-1"),
        float.fromhex("0x1.eaaaaaaaaaaaap-1"),
    ],
])
nodes2 = np.asfortranarray([
    [
        float.fromhex("-0x1.924924924924ap-1"),
        float.fromhex("-0x1.a492492492493p-1"),
        float.fromhex("-0x1.924924924924ap-1"),
    ],
    [
        float.fromhex("0x1.edb6db6db6db7p-1"),
        float.fromhex("0x1.db6db6db6db6ep-1"),
        float.fromhex("0x1.db6db6db6db6ep-1"),
    ],
])

(I will clean this report up shortly at some point, currently in the middle of another task.)

[dhermes]

Three of the four detected intersections are corners and one of these is not exact:

>>> [[v for v in r] for r in edges1[0].intersect(edges2[0])]
[[0.8571428571428565, 1.0], [0.0, 0.16666666666666774]]
>>> [[v for v in r] for r in edges1[0].intersect(edges2[2])]                                                                                                                                                        
[[0.8571428571428579], [0.9999999999999969]]
>>> [[v for v in r] for r in edges1[1].intersect(edges2[2])]                                                                                                                                                        
[[0.1428571428571421], [0.8333333333333307]]

The error is 3.1086244689504383e-15, which is likely below some "round to 0 or 1" threshold.