docs(reviewer): baustein D — close Java-scan + lit-integration gaps

Earlier baustein B (`07c653c`) added a 6-row Research-Alignments table
+ a "what's new" banner, but only surfaced ~75 % of what the four
Java-scan + literature-integration commits (`f854f0e`, `979f30c`,
`e8a118f`, `8daee1b`) had introduced.  This commit closes the gaps
identified in the lückenprüfung:

Research-Alignments table grows from 6 → 10 rows
─────────────────────────────────────────────────
* +quasi-isothermic maps  (Phase 10e, Java port — 6 classes incl.
  discrete Beltrami-field solver, Lawson correspondence ~800 lines)
* +higher-genus + hyperelliptic surfaces (Phase 10b — `HyperellipticUtility`
  + Bobenko–Bücking 2009)
* +Möbius centring as variational problem (Phase 9d.4 — replaces the
  iterative Fréchet-mean fallback in `normalise_hyperbolic()`)
* +Boundary-First / interactive flattening row (Crane 2017 BFF; Stripe
  Patterns 2015) — listed for comparison even though it is not on the
  porting roadmap, so the reader sees we know about it
* table caption clarifies that some rows are RESEARCH-only (no Java
  parent) and some are planned ports

"What's new" banner
───────────────────
* citation count corrected from "+9" to "+13" — the four Tier-2 papers
  added in commit `e8a118f` (Springborn 2019, Springborn–Veselov 2015,
  Crane 2017 BFF, Bonneel et al. 2015 Stripe Patterns) are now named
* phase count of "+6 phases" kept, but +Phase 9d.4 (Möbius centring)
  and +Phase 10e (quasi-isothermic) are now called out explicitly so
  the reader knows what is in the count
* cross-link to `java-parity.md` for the reverse table (every Java
  class → C++ destination or *do-not-port* rationale)

questions.md / Q1
─────────────────
* expand the table from 3 to 6 candidate phases — adding 10e (quasi-
  isothermic), 10b (hyperelliptic), and 9d.4 (Möbius centring) as
  options alongside the existing 9d.2 / 9f / 10c+10c′
* track column distinguishes RESEARCH-only from planned-port
* +Question C — "is there a seventh line we are missing?" — invites
  the reader to flag a research thread we have not scoped yet

Pages hub will be refreshed to v5 in a follow-up step (separate from
the in-repo commit, lives only on the codeberg `pages` branch).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

doc/reviewer/briefing.md

@@ -36,7 +36,9 @@ shows static quality-gate status.
 ## Research alignments — where this library could be infrastructure for your work
 
 The current snapshot already contains, or has roadmap entries for,
-the following:
+the following.  Most rows match an active publication line in
+discrete differential geometry; a few (marked *no Java parent*) are
+research-only phases the reader can shape at design stage.
 
 | Your research thread | What this snapshot has | Phase |
 |---|---|---|
@@ -44,27 +46,43 @@ the following:
 | **Canonical Delaunay tessellations of decorated hyperbolic surfaces** (Lutz 2023, *Geom. Dedicata*; Lutz 2024 PhD thesis) | cut-graph + period matrix + hyperbolic-disk layout as scaffolding; canonical-tessellation algorithm itself outlined | **10c** planned |
 | **Hyperideal polyhedra rigidity** (Bowers–Bowers–Lutz 2026) | HyperIdeal functional + analytic Hessian derivation (805-line LaTeX note) | **9b-analytic** derived; **10c′** KAT planned |
 | **Optimal cone placement / non-Euclidean cone metrics** (Crane et al. 2018) | Cone-singularity port via `ConesUtility` scoped; the *non-Euclidean* extension is the research delta | **9d.1** port + **9d.2** RESEARCH |
-| **Polygon Laplacian on general meshes** (Alexa–Wardetzky 2011; Alexa 2020) | no Java parent; first phase a reviewer can shape at design stage | **9f** RESEARCH (planned) |
+| **Polygon Laplacian on general meshes** (Alexa–Wardetzky 2011; Alexa 2020) | *no Java parent* — first phase a reviewer can shape at design stage | **9f** RESEARCH (planned) |
+| **Quasi-isothermic maps** (generalising conformality where exact conformality is impossible — Lawson-correspondence parameterisation) | scoped as a 6-class port (~800 lines) from the Java original: `QuasiisothermicLayout`, `DBFSolution` (discrete Beltrami field), `SinConditionApplication`, `QuasiisothermicDelaunay`, `QuasiisothermicUtility`, `ConformalStructureUtility` | **10e** planned |
+| **Higher-genus + hyperelliptic surfaces** (Bobenko–Bücking 2009 on polyhedral surfaces; period matrices with block-diagonal Z₂ structure) | port of `HyperellipticUtility` + `HyperIdealHyperellipticUtility` scoped; existing period-matrix code as scaffolding | **10b** planned |
+| **Möbius centring for Poincaré-disk layouts** as a variational problem (Lorentz geometry: `E = Σ log(−⟨x,p⟩/√(−⟨x,x⟩))`) | currently we use iterative Fréchet mean in `normalise_hyperbolic()`; the principled variational alternative is scoped via the Java `MobiusCenteringFunctional` port (full gradient + Hessian) | **9d.4** planned |
+| **Boundary-First / interactive flattening** (Crane et al. 2017 BFF; Bonneel et al. 2015 *Stripe Patterns on Surfaces*) | not on the roadmap as ports; documented in [`references.md`](../math/references.md) as comparison points / inspiration for future API design | — |
 | **Schläfli-based variational machinery** (Rivin–Springborn 1999) | derivation done, implementation gated on your view of whether the ~6× speedup over our block-FD path matters at your mesh sizes | **9b-analytic** ready to implement |
 
-See [`doc/roadmap/research-track.md`](../roadmap/research-track.md)
+See [`doc/roadmap/phases.md`](../roadmap/phases.md) for the per-phase
-for the per-phase acceptance criteria and
+porting plan, [`doc/roadmap/research-track.md`](../roadmap/research-track.md)
-[`doc/roadmap/phases.md`](../roadmap/phases.md) for the porting plan.
+for the items beyond Java parity with explicit acceptance criteria,
+and [`doc/roadmap/java-parity.md`](../roadmap/java-parity.md) for the
+reverse table (every Java class → C++ destination or *do-not-port*
+rationale).
 
 ## What's new on this snapshot (since the previous publish)
 
-- **+6 new porting-roadmap phases** (9d cones / 9e circle-pattern
+- **+6 new porting-roadmap phases** (9d cones + 9d.4 Möbius centring /
-  layout / 10d Koebe circle-domain / 10e quasi-isothermic / 10f Koebe
+  9e circle-pattern layout / 10d Koebe circle-domain / 10e
-  polyhedra / 10g cyclic-symmetry quotients) derived from a full
+  quasi-isothermic / 10f Koebe polyhedra / 10g cyclic-symmetry
-  Java-library scan.
+  quotients) derived from a full Java-library scan.  See `phases.md`
-- **+9 literature citations** integrated into the roadmap, all
+  for the per-phase plan and `java-parity.md` for the reverse table.
-  Tier-1/2 in the research line above (Bobenko–Lutz 2024 IMRN;
+- **+13 literature citations** integrated into the roadmap, all
-  Bobenko–Lutz 2025 DCG; Lutz 2023 Geom. Dedicata; Lutz 2024 PhD;
+  Tier-1/2.  Decorated-DCE / canonical-tessellation / hyperideal line:
-  Bowers–Bowers–Lutz 2026; Crane et al. 2018; Alexa–Wardetzky 2011;
+  Bobenko–Lutz 2024 IMRN; Bobenko–Lutz 2025 *DCG*; Lutz 2023
-  Alexa 2020; Rivin–Springborn 1999).
+  *Geom. Dedicata*; Lutz 2024 PhD; Bowers–Bowers–Lutz 2026.  Cones,
-- **Phase 9f** (polygon Laplacian on general meshes) added as
+  polyhedra, period matrices: Crane et al. 2018; Springborn 2019
+  (hyperbolic polyhedra); Bobenko–Bücking 2009; Rivin–Springborn 1999.
+  Polygon Laplacians: Alexa–Wardetzky 2011; Alexa 2020.  Integrable +
+  practical-flattening context: Springborn–Veselov 2015 (cluster
+  dynamics); Crane et al. 2017 (BFF); Bonneel et al. 2015 (Stripe
+  Patterns).
+- **Phase 9f** (polygon Laplacian on non-triangular meshes) added as
   RESEARCH-only — no Java parent — so you can influence its design
   before it exists.
+- **Phase 10e** (quasi-isothermic maps) and **Phase 9d.4** (variational
+  Möbius centring) newly scoped from the Java scan; both touch
+  research lines adjacent to decorated DCE.
 - **`output_uv_map`** now covers 4 of 5 DCE solvers (Inversive-Distance
   added; CP-Euclidean deferred to Phase 9c with a clear runtime error
   rather than silent failure).

doc/reviewer/questions.md

@@ -21,18 +21,22 @@ These are the seven items that would benefit most from a second opinion.
 
 ---
 
-## Q1 — Research-track alignment: which RESEARCH phase would unblock concrete experiments you want to run?
+## Q1 — Research-track alignment: which RESEARCH or planned phase would unblock concrete experiments you want to run?
 
-Three phases in `doc/roadmap/research-track.md` are research-only
+The roadmap now contains six phases close to live research lines,
-(no Java parent, no immediate user request), but each maps onto a
+each with concrete acceptance criteria (or, for the Java-port phases,
-recognised live research line and each has explicit acceptance
+a clear specification from the Java original).  Three are RESEARCH-only
-criteria:
+(no Java parent, no immediate user request); three are Java-port
+phases whose existence is settled but whose priority is open:
 
-| Phase | What it would add | Closest published line |
+| Phase | Track | What it would add | Closest published line |
-|---|---|---|
+|---|---|---|---|
-| **9d.2** | Decorated DCE in non-Euclidean (spherical + hyperbolic) geometries; Penner coordinates as first-class DOF; automatic cone placement for non-Euclidean targets | Decorated DCE in non-Euclidean geometries (2025, *Discrete Comput. Geom.*); optimal cone singularities for Euclidean flattening (2018, *SIGGRAPH*) |
+| **9d.2** | RESEARCH | Decorated DCE in non-Euclidean (spherical + hyperbolic) geometries; Penner coordinates as first-class DOF; automatic cone placement for non-Euclidean targets | Decorated DCE in non-Euclidean geometries (2025, *Discrete Comput. Geom.*); optimal cone singularities for Euclidean flattening (2018, *SIGGRAPH*) |
-| **9f** | Discrete Laplace–Beltrami on **non-triangular** polygonal meshes (virtual-node / generalised cotangent), making DCE work on quad / Voronoi tessellations without re-triangulation | Polygon Laplacians (2011 *SIGGRAPH* + 2020 *TOG*) |
+| **9f** | RESEARCH | Discrete Laplace–Beltrami on **non-triangular** polygonal meshes (virtual-node / generalised cotangent), making DCE work on quad / Voronoi tessellations without re-triangulation | Polygon Laplacians (2011 *SIGGRAPH* + 2020 *TOG*) |
-| **10c + 10c′** | Canonical Delaunay tessellations of decorated hyperbolic surfaces; Koebe polyhedron realisation (KAT) with rigidity-aware Newton | Canonical tessellations of decorated hyperbolic surfaces (2023, *Geom. Dedicata*); rigidity of circle / hyperideal polyhedra (2026, preprint) |
+| **10c + 10c′** | planned | Canonical Delaunay tessellations of decorated hyperbolic surfaces; Koebe polyhedron realisation (KAT) with rigidity-aware Newton | Canonical tessellations of decorated hyperbolic surfaces (2023, *Geom. Dedicata*); rigidity of circle / hyperideal polyhedra (2026, preprint) |
+| **10e** | planned | Quasi-isothermic maps (~800 lines Lawson-correspondence) — generalises conformality to meshes where exact conformality is impossible.  Six new classes including a discrete Beltrami-field solver. | Java original `QuasiisothermicUtility` line; no obvious single-paper reference in the existing literature index |
+| **10b** | planned | Hyperelliptic surfaces (genus g ≥ 2 with Z₂ symmetry); period matrices with block-diagonal structure; Penner-coordinate variant via `HyperIdealHyperellipticUtility` | Bobenko–Bücking 2009 *Conformal Structures and Period Matrices of Polyhedral Surfaces* |
+| **9d.4** | planned | Möbius centring of Poincaré-disk layouts as a *variational* problem (Lorentz energy with full gradient + Hessian), replacing today's iterative Fréchet-mean fallback in `normalise_hyperbolic()` | Java original `MobiusCenteringFunctional`; closest published context: decorated-DCE Möbius normalisation, also used in canonical-tessellation post-processing |
 
 **Question A:** which of these (if any) would unblock concrete
 numerical experiments you have wanted to run but currently have no
@@ -42,10 +46,17 @@ reference implementation for?
 target the *next* milestone after Phase 9c, or is there a different
 order that would serve your research better?
 
+**Question C:** is there a *seventh* line we are missing — a research
+thread close to your own where you would want infrastructure that the
+table above does not yet cover?
+
 Context:
 [`research-track.md`](../roadmap/research-track.md) §"Non-Euclidean
-cone extensions" and §"Polygon Laplacian"; the integrated literature
+cone extensions" and §"Polygon Laplacian";
-sits in [`math/references.md`](../math/references.md).
+[`phases.md`](../roadmap/phases.md) for the per-phase porting plan;
+[`java-parity.md`](../roadmap/java-parity.md) for the reverse Java
+class table; the integrated literature sits in
+[`math/references.md`](../math/references.md).
 
 ---