fix(citations): correct Kolpakov-Mednykh misattribution → Springborn 2008

arXiv:math/0603097 is Springborn 2008 ("A variational principle for weighted
Delaunay triangulations and hyperideal polyhedra"), not a Kolpakov-Mednykh paper.
The author pair Kolpakov & Mednykh has no joint publication from 2006; their
earliest collaboration is arXiv:1008.0312 (2010, on torus knots, unrelated).

The wrong author name was introduced during the Java→C++ port — the Java source
correctly links to math/0603097 without naming the authors; whoever ported it
invented "Kolpakov-Mednykh". The S1 citation audit (2026-05-31) then cemented
the error by adding the incorrect row to references.md.

Files corrected (7):
- code/include/hyper_ideal_utility.hpp
- code/include/hyper_ideal_functional.hpp
- code/tests/cgal/test_hyper_ideal_functional.cpp
- doc/math/references.md
- doc/roadmap/research-track.md
- doc/architecture/project-structure.md
- doc/api/tests.md

Also:
- doc/reviewer/math-derivation-citation-audit-2026-05-31.md: M1 post-correction noted
- doc/reviewer/finding-orchestration.md: lesson-learned section added (AI citation
  audits can introduce plausible-but-wrong attributions; human expert review required
  before CGAL submission)
- papers/MANUAL-DOWNLOAD.md: overview of papers requiring manual download (paywalled
  journals, TU Berlin theses, books)
- .gitignore: papers/*.pdf excluded (downloaded arXiv PDFs, not tracked)

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

code/include/hyper_ideal_functional.hpp

@@ -375,7 +375,7 @@ static FaceAngles compute_face_angles(
 ///
 /// Supported configurations (faithful port of HyperIdealFunctional.java):
 ///   * All three vertices hyper-ideal (v?b = true)       → Meyerhoff/Ushijima volume
-///   * Exactly one vertex ideal (v?b = false, other two true) → Kolpakov-Mednykh volume
+///   * Exactly one vertex ideal (v?b = false, other two true) → Springborn 2008 volume
 ///
 /// NOT supported — faces with two or three ideal vertices.  The Java reference
 /// (HyperIdealFunctional.java lines 222-231) uses an if/else-if chain that

code/include/hyper_ideal_utility.hpp

@@ -77,7 +77,7 @@ inline double calculateTetrahedronVolume(double A, double B, double C,
 }
 
 /// Volume of a hyperideal tetrahedron with one ideal vertex at γ via
-/// the Kolpakov-Mednykh formula (arxiv math/0603097).  Same as Java
+/// the Springborn 2008 formula (arxiv math/0603097).  Same as Java
 /// `HyperIdealUtility.calculateTetrahedronVolumeWithIdealVertexAtGamma()`.
 inline double calculateTetrahedronVolumeWithIdealVertexAtGamma(
     double gamma1, double gamma2, double gamma3,

code/tests/cgal/test_hyper_ideal_functional.cpp

@@ -267,7 +267,7 @@ TEST(HyperIdealFunctional, MultiIdealGuard_AllThreeIdealVertices_Throws)
 TEST(HyperIdealFunctional, MultiIdealGuard_ExactlyOneIdeal_DoesNotThrow)
 {
     // Exactly one ideal vertex per face must NOT throw — it is the supported
-    // one-ideal-vertex configuration (Kolpakov-Mednykh formula).
+    // one-ideal-vertex configuration (Springborn 2008 formula).
     auto mesh = make_triangle();
     auto maps = setup_hyper_ideal_maps(mesh);