docs(references): M1/M2/M4 citation fixes (audit quick-wins)
M1: Add two missing references used in hyper_ideal_utility:
- Kolpakov, Mednykh (2006, arXiv math/0603097) — tetrahedron volume w/ one ideal vertex
- Meyerhoff, Ushijima (2006) — tetrahedron volume w/ three ideal vertices
M2: Clarify BPS publication year: Geometry & Topology 2015 (arXiv 2010)
- Update references.md to note "first posted 2010"
- Normalize all code comments from "BPS-2010" → "BPS-2015" (published version)
M4: Standardize citation format in code comments
- Normalize all "Luo (2004)" / "Luo-2004" / "Luo's 2004" → "Luo 2004"
- Matches references.md convention: Author Year (no parens/dashes)
282/282 tests pass. Addresses M1, M2, M4 from math-derivation-citation audit.
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
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