fix(citations): correct Meyerhoff/Ushijima misattribution

DOI 10.1007/0-387-29555-0_13 is Ushijima (sole author) —
"A Volume Formula for Generalised Hyperbolic Tetrahedra",
in: Prékopa & Molnár (eds.), Non-Euclidean Geometries,
Springer 2006. arXiv: math/0309216.

The references.md entry was wrong on all three counts:
  - Author:  "Meyerhoff, Ushijima" → Ushijima only
  - Title:   "A Note on the Dirichlet Domain" → entirely different title
  - Book:    "The Epstein Birthday Schrift" → Non-Euclidean Geometries

Same error pattern as the Kolpakov-Mednykh fix: the Java source
links only to a DOI without naming authors; a wrong name was
invented during the C++ port.

Files corrected: hyper_ideal_utility.hpp, hyper_ideal_functional.hpp,
references.md, tests.md, project-structure.md, finding-orchestration.md,
math-derivation-citation-audit.md, MANUAL-DOWNLOAD.md

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

doc/reviewer/math-derivation-citation-audit-2026-05-31.md

@@ -68,8 +68,8 @@ load-bearing formula with no entry.
 
 ### Fix
 Add a `references.md` row: Kolpakov, Mednykh — *(full title)*, arXiv `math/0603097`,
-mapped to `hyper_ideal_utility.hpp`. Likewise confirm the Meyerhoff / Ushijima 2006
-volume reference (cited in code) has a row.
+mapped to `hyper_ideal_utility.hpp`. Ushijima 2006 (DOI 10.1007/0-387-29555-0_13, arXiv math/0309216) has a row —
+sole author is Ushijima; "Meyerhoff" is not a co-author (corrected 2026-06-04).
 
 ### Acceptance criteria
 - Every formula cited inline in `code/include/` has a matching `references.md` entry.