docs: citation audit + correct 8 mis-citations; add Phases 12/13

External reviewer pass over the literature references. Verified entries
against arXiv/DOI/publisher and corrected misattributions that had
propagated across the docs.

Corrected citations (consistent across all docs):
- Bowers-Bowers-Lutz 2026: title was the 2017 paper's
  -> "Rigidity of Koebe Polyhedra and Inversive Distance Circle Packings"
- Liouville theorem: "Springborn 2019" -> Pinkall & Springborn,
  Geom. Dedicata 214 (2021)
- Bobenko-Pinkall-Springborn: "G&T 14 (2010)" -> G&T 19(4) (2015), 2155-2215
- Optimal Cone Singularities: "Crane, Soliman, Ben-Chen, Schroeder"
  -> Soliman, Slepcev, Crane, ACM TOG 37(4)
- Schlaefli formula: "Rivin, Springborn 1999" -> Rivin, Schlenker
- Quasiconformal distortion: "Springborn, Veselov" -> Born, Buecking,
  Springborn (arXiv:1505.01341)
- Period matrices: "Bobenko, Buecking 2009" (was Bobenko-Mercat-Schmies'
  title) -> Bobenko-Mercat-Schmies 2011 + genuine Bobenko-Buecking 2021
- Fabricated entry: "Alexa 2020, DOI 10.1145/3414685.3417840" pointed to
  an unrelated paper (Pixelor) -> Bunge, Herholz, Kazhdan, Botsch 2020
- Stripe Patterns: "Bonneel et al. 2015" -> Knoeppel, Crane, Pinkall,
  Schroeder 2015

Equation-number corrections (verified against the PDFs):
- Glickenstein 2011 "eq. 4.6" -> "§5.2" (no such equation label exists)
- Springborn 2020 "eq. 4.6" -> "§4 variational gradient"
- inversive-distance attribution softened to classical inversive distance

Other:
- DBFEnergy bibliography (separate repo) and convergence half-sentence in
  novelty-statement.md §3.3 (Bobenko-Buecking 2021)
- Status legend (implemented vs planned) at top of references.md
- New Phase 12 (decorated DCE & geometric transition, Chain A, near-term)
  and Phase 13 (canonical tessellations & polyhedral realisation, Chain B
  capstone) in phases.md + research-track.md; 10c scope-boundary note
  clarifying infrastructure vs Lutz-specific algorithms

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

doc/tutorials/add-inversive-distance.md

@@ -78,7 +78,7 @@ the domain where every triangle is valid); we use the same 10-point
 Gauss-Legendre quadrature as `euclidean_functional.hpp`.
 
 The Hessian is finite-difference for the MVP; an analytic form
-(Glickenstein 2011 eq. 4.6) is documented in the research-track roadmap.
+(Glickenstein 2011 §5.2) is documented in the research-track roadmap.
 
 ---
 

doc/tutorials/block-fd-hessian.md

@@ -107,7 +107,7 @@ controlling the degenerate-vertex clamps inherited from
 The global gradient is the angle-defect / Schläfli-type sum
 
 ```
-G_{b,v} =  Σ_{f ∋ v}  β_v(f)  −  Θ_v                          (Springborn 2020 eq. 4.6)
+G_{b,v} =  Σ_{f ∋ v}  β_v(f)  −  Θ_v                          (Springborn 2020 §4, variational gradient)
 G_{a,e} =  Σ_{f ∋ e}  α_e(f)  −  θ_e
 ```