feat: output_uv_map for InversiveDistance, error for CP-Euclidean, reviewer trio

Three reviewer-meeting deliverables in one commit.

(1) output_uv_map for the two remaining DCE entries
    ─────────────────────────────────────────────────
    * Discrete_inversive_distance.h: full implementation.  After Newton,
      reconstruct effective Euclidean edge lengths from the converged
      log-radii via the Bowers-Stephenson identity
      `ℓᵢⱼ² = rᵢ² + rⱼ² + 2·Iᵢⱼ·rᵢ·rⱼ`, populate a temporary
      EuclideanMaps with `lambda0 = log(ℓᵢⱼ²)`, and reuse the existing
      `euclidean_layout(mesh, 0, eucl)` priority-BFS.  Per-vertex
      Point_2 coordinates written into the user-supplied pmap.
      Optional `normalise_layout(true)` applies the canonical PCA
      centroid + major-axis rotation, same as the other 3 entries.

    * Discrete_circle_packing.h: throws std::runtime_error with a
      clear pointer to Phase 9c rather than silently producing
      nonsense.  CP-Euclidean is face-based; the faithful output is a
      per-face circle packing in ℝ², not a per-vertex Point_2 map.
      A true layout requires BPS-2010 §6 (~150 lines, on the porting
      roadmap as Phase 9c).  Failing loudly is the honest default.

    Tests: 2 new cases in test_cgal_phase8b_lite.cpp
    (OutputUvMap_InversiveDistance_PopulatesPmap;
    OutputUvMap_CPEuclidean_ThrowsClearly).  Both green.
    Suite total now 259 (was 257, +2).  CGAL subtotal: 234 → 236.

(2) Reviewer meeting documents
    ──────────────────────────
    New directory doc/reviewer/ with three files:

    * briefing.md  — one-page orientation for the reviewer.
      What the project is, where to look first
      (https://tmoussa.codeberg.page/ConformalLabpp/), the headline
      evidence (tests/coverage/sanitizers/license), what we want from
      them, what's deferred and why, and the 5 questions in a separate
      file.

    * questions.md — the 5 concrete decisions we want their second
      opinion on:
        Q1 Phase 9c (port-literal vs re-derive)
        Q2 Phase 9b-analytic (worth ~2 weeks for ~6× speedup?)
        Q3 CP-Euclidean output_uv_map (build now or defer?)
        Q4 CGAL submission strategy (one package or five?)
        Q5 geometry-central cross-validation co-authorship
      Plus an explicit "what would you say no to?" question at the
      bottom — negative feedback is the highest-value information.

    * agenda.md   — my own internal playbook (NOT to be sent).
      60-min flow: 5-min thank-you, 10-min architecture tour,
      30-min for Q1-Q5 in the order Q4-Q1-Q2-Q5-Q3, 5-min "no"
      question, 5-min wrap-up.  Includes post-meeting memo template
      to fill out in the 30 min after.

    * README.md    — index for the directory; says which file goes
      to whom and when to send.

(3) locked-vs-flexible.md known-limitations update
    ─────────────────────────────────────────────
    "output_uv_map covers 3 of 5 entries" → "covers 4 of 5".
    CP-Euclidean's throws-clearly behaviour documented as a Phase 9c
    deliverable rather than a passive gap.

Bonus: extended .codespellrc ignore list (acknowledgement, the
British-English spelling I used in agenda.md).

Verifications on this commit:
  259/259 tests pass (0 skipped)
  scripts/check-test-counts.sh:                OK (23 + 236 = 259)
  scripts/quality/license-headers.sh:          OK (66/66 SPDX)
  python3 scripts/quality/cgal-conventions.py: OK (0/6 violations)
  scripts/quality/codespell.sh:                OK (0 typos)
  scripts/quality/shellcheck.sh:               OK (0 findings)
  python3 scripts/check-markdown-links.py:     OK (143/143)

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

doc/reviewer/agenda.md

@@ -0,0 +1,114 @@
+# Reviewer meeting — agenda (for me)
+
+> **Audience.** Myself, before the meeting. Not shared with the
+> reviewer (they have [`briefing.md`](briefing.md) and
+> [`questions.md`](questions.md) instead).
+>
+> **Purpose.** Keep the conversation on the high-stakes items
+> without slipping into detail-tour mode.
+
+**Length:** ~60 min (default; willing to extend if conversation is
+productive).
+
+## Opening — 5 min
+
+- **Thank-you** + ~30 s on why I value their time specifically
+  (Springborn/Bobenko background = best-positioned audience for
+  this material).
+- **Confirm format**: they've read `briefing.md`? Yes → skip ahead.
+  No → take 3 min to walk through it together via the reviewer-hub
+  URL.
+
+## §1 Architectural tour — 10 min
+
+Goal: they leave §1 with a mental map of what's where.
+
+1. Open <https://tmoussa.codeberg.page/ConformalLabpp/>.
+2. Click through:
+   - Doxygen → `discrete_conformal_map_euclidean` (the canonical entry,
+     shows the named-parameter pattern + traits).
+   - `locked-vs-flexible.md` § Summary table.
+   - `dependencies.md` § TL;DR.
+3. **Don't** demo running the test suite live unless they ask —
+   they can verify the green badges later.
+
+**Cue to move on**: when they have no more "where is X?" questions.
+
+## §2 The five questions — 30 min
+
+Goal: get clear answers to as many of the 5 questions in
+[`questions.md`](questions.md) as possible.  Order matters:
+
+1. **Q4 first** (CGAL submission strategy — single package vs five).
+   This sets the framing for the rest.  ~5 min.
+2. **Q1** (Phase 9c port-literal vs re-derive).  ~5 min.
+3. **Q2** (Phase 9b-analytic — is the 6× speedup worth ~2 weeks?).
+   May trigger longer math discussion; cap at 10 min and offer to
+   continue async.
+4. **Q5** (GC-1 cross-validation co-authorship).  ~5 min.
+5. **Q3** (CP-Euclidean output_uv_map).  ~5 min.
+
+**Trap to avoid**: don't relitigate any of the already-made decisions
+(e.g. Surface_mesh as default, Eigen as backend) unless they bring it
+up under "anything you'd say no to".  Move forward, not sideways.
+
+## §3 The "no" question — 5 min
+
+Last paragraph of [`questions.md`](questions.md): *"Is there one
+architecture decision where you think 'no, that's the wrong call'?"*
+
+Ask explicitly. Wait.  Don't fill silence.  Negative feedback at this
+phase is the highest-value information of the entire meeting.
+
+## §4 Wrap-up — 5 min
+
+- **Summarise**: 1 sentence per Q1–Q5 answer.
+- **Next steps**: 
+  - Items they offered to help on (if any) → I'll send a follow-up
+    email within 48 h.
+  - Items they flagged as worth changing → I'll write a one-page
+    plan + send for sign-off before starting work.
+- **Cadence**: do they want a periodic update? Once-a-quarter? When
+  hitting Phase 9c milestone?
+- **Citation**: ask whether they want acknowledgement in the
+  CGAL submission's `THANKS.md`.
+
+## Material I have ready (in tabs)
+
+1. <https://tmoussa.codeberg.page/ConformalLabpp/>
+2. <https://codeberg.org/TMoussa/ConformalLabpp> (source)
+3. Local terminal in the repo (for any "show me X" requests)
+4. `doc/math/hyperideal-hessian-derivation.md` open in editor
+   (for Q2)
+5. `doc/architecture/locked-vs-flexible.md` open at "Summary table"
+6. This file, [`questions.md`](questions.md), and
+   [`briefing.md`](briefing.md) for backstop.
+
+## After the meeting
+
+- 30-min decompression — don't take notes during the meeting beyond
+  bullet-tracking of Q1–Q5 answers; write up a full memo in the 30 min
+  AFTER.
+- Memo template:
+  ```
+  Date:  ____
+  Reviewer:  ____
+  Duration:  ____ min
+  
+  Q1 answer:  ____
+  Q2 answer:  ____
+  Q3 answer:  ____
+  Q4 answer:  ____
+  Q5 answer:  ____
+  "No" pointer:  ____
+  
+  Action items:
+    [ ] (within 48 h)  ____
+    [ ] (within 2 wks) ____
+    [ ] (longer term)  ____
+  
+  Cadence agreed:  ____
+  ```
+
+- Store the memo at `doc/reviewer/2026-XX-XX-meeting-notes.md`
+  (gitignored if confidential, otherwise committed).