release: v0.9.0 — finalise PR #11 with CHANGELOG, version bump, stub cleanup

Closes the v0.9.0 release loop on top of Phase 9a-Newton + Phase 8b-Lite:

* CHANGELOG.md (NEW) — Keep-A-Changelog format, with v0.9.0 entry
  detailing all Phase 9a / 9b / 8b-Lite contents and the doc-audit
  corrections that landed via PR #10.

* CITATION.cff — version 0.7.0 → 0.9.0, date 2026-05-18 → 2026-05-22.

* Stale HDS-port stubs removed (13 GTEST_SKIPs total):
  - code/tests/test_spherical_functional.cpp
  - code/tests/test_hyper_ideal_functional.cpp
  - code/tests/test_hyper_ideal_hyperelliptic_utility.cpp
  These referenced a "HDS port (Phase 4)" that never happened —
  CoHDS was intentionally replaced by CGAL::Surface_mesh, and the
  functional tests live in code/tests/cgal/test_*_functional.cpp.

* Test-count updates everywhere:
  - Non-CGAL  36 → 23  (drop = 13 deleted stubs)
  - CGAL      176 → 227
  - Total     212 → 250  (+38 net, 0 skipped)
  Files: README.md, CLAUDE.md, CHANGELOG.md, scripts/try_it.sh,
         doc/api/tests.md, doc/contributing.md, doc/getting-started.md,
         doc/math/validation.md.

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

code/tests/CMakeLists.txt

@@ -1,5 +1,5 @@
 add_executable(conformallab_tests
-    # ── Fully ported (pure math, no HDS) ────────────────────────────────────
+    # ── Pure-math test suite (no CGAL, no mesh — runs on every branch) ─────
     test_clausen.cpp
     test_hyper_ideal_utility.cpp
     test_matrix_utility.cpp
@@ -7,12 +7,14 @@ add_executable(conformallab_tests
     test_discrete_elliptic_utility.cpp
     test_p2_utility.cpp
     test_hyper_ideal_visualization_utility.cpp
-
-    # ── Stubs: blocked until HDS port (Phase 4) ──────────────────────────────
-    # All tests call GTEST_SKIP() with a clear explanation.
-    test_hyper_ideal_functional.cpp
-    test_hyper_ideal_hyperelliptic_utility.cpp
-    test_spherical_functional.cpp
+    #
+    # Stale stub files were removed in v0.9.0:
+    #   test_hyper_ideal_functional.cpp
+    #   test_hyper_ideal_hyperelliptic_utility.cpp
+    #   test_spherical_functional.cpp
+    # They referenced a "HDS port (Phase 4)" that never happened —
+    # CoHDS was intentionally replaced by CGAL::Surface_mesh, and the
+    # functionals + tests live in code/tests/cgal/test_*_functional.cpp.
 )
 
 target_include_directories(conformallab_tests SYSTEM PRIVATE

code/tests/test_hyper_ideal_functional.cpp

@@ -1,37 +0,0 @@
-// 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)";
-}

code/tests/test_hyper_ideal_hyperelliptic_utility.cpp

@@ -1,26 +0,0 @@
-// Stub for de.varylab.discreteconformal.functional.HyperIdealHyperellipticUtilityTest.
-//
-// STATUS: BLOCKED – requires HDS port (Phase 4).
-//
-// Tests compute intersection angles of circles associated with hyper-ideal
-// vertices using CoHDS + HalfEdgeUtils.  All three tests operate on mesh
-// data structures that are not yet available in C++.
-//
-// Java tests and their status:
-//   testCalculateCircleIntersections         – blocked: needs CoHDS + HalfEdgeUtils
-//   testCalculateCircleIntersectionsInfinite – blocked: needs CoHDS + HalfEdgeUtils
-//   testLawsonHyperellipticAngles            – blocked: needs CoHDS + HyperIdealGenerator
-
-#include <gtest/gtest.h>
-
-TEST(HyperIdealHyperellipticUtilityTest, CalculateCircleIntersections) {
-    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + HalfEdgeUtils)";
-}
-
-TEST(HyperIdealHyperellipticUtilityTest, CalculateCircleIntersectionsInfinite) {
-    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + HalfEdgeUtils)";
-}
-
-TEST(HyperIdealHyperellipticUtilityTest, LawsonHyperellipticAngles) {
-    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + HyperIdealGenerator)";
-}

code/tests/test_spherical_functional.cpp

@@ -1,37 +0,0 @@
-// Stub for de.varylab.discreteconformal.functional.SphericalFunctionalTest (Java/JUnit).
-//
-// STATUS: BLOCKED – requires HDS port (Phase 4).
-//
-// Tests evaluate gradient and Hessian of the SphericalFunctional on meshes
-// built via CoHDS + ConvexHull, and check that a regular spherical metric
-// is a critical point of the functional.  All tests require the HalfEdge
-// data structure and the functional evaluation framework in C++.
-//
-// Java tests and their status:
-//   testReducedGradient   – blocked: needs CoHDS + SphericalFunctional
-//   testReducedHessian    – blocked: needs CoHDS + SphericalFunctional
-//   testGradient          – blocked: needs CoHDS + SphericalFunctional
-//   testHessian           – blocked: needs CoHDS + SphericalFunctional
-//   testCriticalPoint     – blocked: needs CoHDS + ConvexHull + SphericalFunctional
-
-#include <gtest/gtest.h>
-
-TEST(SphericalFunctionalTest, ReducedGradient) {
-    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + SphericalFunctional)";
-}
-
-TEST(SphericalFunctionalTest, ReducedHessian) {
-    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + SphericalFunctional)";
-}
-
-TEST(SphericalFunctionalTest, Gradient) {
-    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + SphericalFunctional)";
-}
-
-TEST(SphericalFunctionalTest, Hessian) {
-    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + SphericalFunctional)";
-}
-
-TEST(SphericalFunctionalTest, CriticalPoint) {
-    GTEST_SKIP() << "Blocked: requires HDS port (CoHDS + ConvexHull + SphericalFunctional)";
-}