test(hyperideal): Tier-3 Lawson square-tiled golden-vector Java cross-validation

Ports the Java HyperIdealConvergenceTest (Lawson square-tiled) — the strongest
remaining @Ignore'd oracle (a hard-coded converged solution from a historical
x86 PETSc run).

- make_lawson_square_tiled(): builds the genus-2 base (4 vertices, 12 edges,
  6 quads) via the low-level CGAL Surface_mesh half-edge API (add_edge +
  set_target/set_next/set_face/set_halfedge), since the multi-edges (≥2 edges
  per vertex pair) make add_face / OFF / polygon-soup impossible. Then
  triangulate_faces → 12 triangles, 18 edges (12 original + 6 diagonals).
  BuildsValidGenus2Mesh: is_valid + V=4/F=12/E=18 + χ=−2.
- ConvergenceGoldenVector_JavaXVal: Θ_v=2π, θ_e=π/2 (12 original edges),
  θ_e=π (6 diagonals); newton_hyper_ideal converges (from x0=1.0, unconstrained)
  to the Java golden vector:
    vertices → 1.1462158341786262
    original → 1.7627471737467797
    aux      → 2.633915794495759
  asserted per symmetry class @1e-5 (robust to DOF ordering).

The perfect symmetry of the golden vector means any consistent one-diagonal
triangulation reproduces the three values, so the external jtem Triangulator
choice need not be replicated. Resolves the Tier-3 item from PR #29's analysis.

242/242 cgal tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

code/tests/cgal/CMakeLists.txt

@@ -86,6 +86,10 @@ add_executable(conformallab_cgal_tests
     #    newton_inversive_distance (FD Hessian).
     test_newton_phase9a.cpp
 
+    # ── Tier-3 Java cross-validation: Lawson square-tiled HyperIdeal ─────────
+    #    Low-level half-edge genus-2 generator + golden-vector convergence.
+    test_lawson_hyperideal.cpp
+
     # ── Phase 8b-Lite: CGAL entry wrappers for the 4 non-Euclidean modes ─────
     #    Spherical, HyperIdeal, CircleP-Euclidean, Inversive-Distance via
     #    <CGAL/Discrete_*.h> public API + Conformal_layout.h wrapper.