tests: port DiscreteEllipticUtility + P2 tests; stub HDS-blocked tests

Fully ported (pure math, no HDS required):
  test_discrete_elliptic_utility.cpp  – 2 tests
    normalizeModulus: move tau into SL(2,Z) fundamental domain
  test_p2_utility.cpp                 – 3 tests
    P2 projective geometry (perpendicularBisector, pointFromLines,
    makeDirectIsometryFromFrames double vs long double precision)

New headers:
  include/discrete_elliptic_utility.hpp  – normalizeModulus
  include/p2_utility.hpp                 – P2 Euclidean geometry (templated
    on scalar type so double and long double share one implementation)

Stubs (GTEST_SKIP, blocked until HDS port – Phase 4):
  test_hyper_ideal_functional.cpp          – 5 tests (1 @Ignore in Java)
  test_hyper_ideal_hyperelliptic_utility.cpp – 3 tests
  test_spherical_functional.cpp            – 5 tests
  All use CoHDS + HalfEdgeUtils which are not yet ported to C++.

Result: 34 tests total | 21 passed | 13 skipped | 0 failed

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

code/tests/test_hyper_ideal_functional.cpp

@@ -0,0 +1,37 @@
+// Stub for de.varylab.discreteconformal.functional.HyperIdealFunctionalTest (Java/JUnit).
+//
+// STATUS: BLOCKED – requires HDS port (Phase 4).
+//
+// These tests evaluate gradient and Hessian of the HyperIdealFunctional on
+// actual mesh data (CoHDS + HyperIdealGenerator).  They cannot be ported
+// until the HalfEdge data structure (CoHDS), the functional evaluation
+// framework, and the mesh generators are available in C++.
+//
+// Java tests and their status:
+//   testHessian()                           – @Ignore in Java (skipped here too)
+//   testGradientWithHyperIdealAndIdealPoints – blocked: needs HDS
+//   testGradientInTheExtendedDomain          – blocked: needs HDS
+//   testGradientWithHyperellipticCurve       – blocked: needs HDS
+//   testFunctionalAtNaNValue                 – blocked: needs HDS
+
+#include <gtest/gtest.h>
+
+TEST(HyperIdealFunctionalTest, TestHessian_IgnoredInJava) {
+    GTEST_SKIP() << "@Ignore in Java – skipped here too";
+}
+
+TEST(HyperIdealFunctionalTest, GradientWithHyperIdealAndIdealPoints) {
+    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + HyperIdealFunctional)";
+}
+
+TEST(HyperIdealFunctionalTest, GradientInTheExtendedDomain) {
+    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + HyperIdealFunctional)";
+}
+
+TEST(HyperIdealFunctionalTest, GradientWithHyperellipticCurve) {
+    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + HyperIdealFunctional)";
+}
+
+TEST(HyperIdealFunctionalTest, FunctionalAtNaNValue) {
+    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + HyperIdealFunctional)";
+}