test: add degenerate-triangle limiting-angle and edge-DOF guard tests
Finding-F and Finding-G from doc/reviewer/external-audit-2026-05-30.md
(java-port-audit missing-test items 1 and 2).
Finding-F — Degenerate triangle: limiting angles (item 1)
test_euclidean_functional.cpp:
DegenerateTriangle_LimitingAngles_L{12,23,31}TooLong
— verifies α_opposite = π, other two = 0, valid = false
for all three edge-over-long cases
DegenerateTriangle_GradientPicksUpPiCorner
— end-to-end mesh test: forces effective l12 >> l23+l31 via
lambda0, evaluates gradient, asserts G_v3 = π (not 2π from
a skipped degenerate face) and G_v1=G_v2 = 2π
test_spherical_functional.cpp:
DegenerateTriangle_LimitingAngles_S{12,23,31}TooLong
— same coverage for spherical_angles()
Finding-G — euclidean_hessian edge-DOF guard (item 2)
test_euclidean_hessian.cpp:
EdgeDOFGuard_Throws
— assign_euclidean_all_dof_indices + euclidean_hessian → throw
EdgeDOFGuard_VertexOnlyDoesNotThrow
— vertex-only layout → no throw (regression guard)
275/275 CGAL tests pass, 0 failed.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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