Fix direction bugs in #addTriangular

[a6b8]

Three bugs in #addTriangular cause incorrect forward/switch direction data in tokenId:

1. Sort comparator compares struct['order'] - struct['order'] (always NaN) instead of a['order'] - b['order']
2. Case 1: acc[0] references full array instead of direction string acc[0][1], and arr[1] references currentPair instead of previous pair acc[0][0]
3. Case 2: arr[2] references currentPair instead of first pair arr[0]

Triangle detection count is unaffected, but traversal direction metadata is wrong.