test: Java golden-value oracles for the five DCE math cores + P1-2/P1-3 fixes

Add bit-for-bit (1e-12) golden-value oracle tests pinning the C++ pure-math
and functional cores against the compiled upstream Java library (openjdk 17):

- HyperIdealGoldenJava: Clausen/Л/ImLi2, ζ13/14/15/ζ, both tetrahedron-volume
  formulas (real de.varylab…Clausen / HyperIdealUtility).
- EuclideanGoldenJava / SphericalGoldenJava: angle formulas + β relations + Л
  energy terms, plus FULL-MESH oracles driving the real EuclideanCyclicFunctional
  / SphericalFunctional on a shared tetrahedron — per-vertex gradient (Θ−Σα) and
  ΔE = E(x)−E(0) (C++ Gauss-Legendre path integral vs Java closed form).
- SphericalGoldenJava.FullMeshEdgeDofGradient: edge-DOF gradient (vertex + edge
  components, α_opp⁺+α_opp⁻−θ_e) vs raw conformalEnergyAndGradient — locks
  Finding 3 at the solution level (audit items 4 & 5).
- PeriodMatrix.NormalizeModulus_GoldenJava: τ-reduction fold convention vs the
  real DiscreteEllipticUtility.normalizeModulus (audit items 7 & 8).

Subtlety documented: the spherical oracles call Java's raw
conformalEnergyAndGradient, not evaluate() (which pre-runs a Brent gauge
maximization that C++ factors into the Newton solver's spherical_gauge_shift).

Also:
- P1-2 (layout.hpp): Euclidean holonomy now uses a per-cut-edge rigid-motion fit
  g(z)=a·z+b, exposing residual_rotation = |arg(a)| as a diagnostic; non-
  regressive (flat case a=1 reduces to the old midpoint formula).
- P1-3 (period_matrix.hpp): is_in_fundamental_domain fixed to the correct
  half-open SL(2,ℤ) domain (−½ ≤ Re < ½). Updated the now-exposed
  ComputePeriodMatrix_ReducedTau_InFD to assert the normalizeModulus domain
  (closed +½ edge) instead.

Test counts (single source of truth = doc/api/tests.md): 272/272 pass, 0
skipped (26 non-CGAL + 246 CGAL).

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

code/include/period_matrix.hpp

@@ -114,11 +114,18 @@ inline std::complex<double> reduce_to_fundamental_domain(std::complex<double> ta
 // is_in_fundamental_domain — check membership in F with tolerance tol.
 // ─────────────────────────────────────────────────────────────────────────────
 /// `true` iff `τ` lies inside the standard SL(2,ℤ) fundamental domain
-/// with tolerance `tol`.
+/// `F = { Im τ > 0, −½ ≤ Re τ < ½, |τ| ≥ 1 }` with tolerance `tol`.
+///
+/// This is the half-open domain produced by `reduce_to_fundamental_domain`
+/// (the right boundary `Re τ = +½ ≡ −½` is excluded via `T`).  It is NOT the
+/// mirror-folded `0 ≤ Re τ ≤ ½` domain produced by `normalizeModulus` (used
+/// inside `compute_period_matrix`); a τ with `Re τ < 0` is a legitimate member
+/// of `F` here but would be folded to `Re ≥ 0` by `normalizeModulus`.
 inline bool is_in_fundamental_domain(std::complex<double> tau, double tol = 1e-9)
 {
     if (tau.imag() <= 0.0) return false;
-    if (std::abs(tau.real()) > 0.5 + tol) return false;
+    if (tau.real() < -0.5 - tol) return false;  // left boundary closed
+    if (tau.real() >  0.5 - tol) return false;  // right boundary Re = +½ excluded (≡ −½)
     if (std::abs(tau) < 1.0 - tol) return false;
     return true;
 }