Harden DDG core and add interactive web workbench

[ryanwhois]

Summary

This v1.2.0 candidate hardens the numerical/topological foundation and adds the repository's first complete interactive web workbench.

Core and algorithms

• construct explicit boundary halfedges and closed boundary loops in C++ and C#
• validate indices, duplicate directed edges, non-manifold edges, pointer relations, and degenerate faces
• assemble symmetric cotangent Laplacians from opposite-angle weights
• add reusable Dirichlet-constrained Poisson solves
• include boundary angle defects in Gaussian curvature
• implement the C# Heat Method weak-divergence stage
• use ordered chord-length boundaries for harmonic disk parameterisation
• make the deferred true-LSCM path fail explicitly instead of mislabelling a harmonic map

Tooling and web

• add a dependency-free Python OBJ topology inspector and four tests
• repair oriented WASM fixtures and Node compatibility
• add the responsive DDG workbench with JS fallback and optional WASM support
• add Vercel root/workbench routing
• update versioning, roadmap, implementation audit, release gates, and changelog

Local verification

• Python inspector: 4/4 tests pass; CLI help exits successfully
• JavaScript syntax and Vercel JSON validation pass
• workflow YAML parses successfully
• all C++ core, algorithm, utility, and demo translation units compile under C++17
• native C++ open-disk smoke passes: boundary loop, Euler characteristic, Laplacian symmetry/row sums, Gauss–Bonnet, constrained UV solve, and Heat Method
• C# sources compile with the .NET 8 Roslyn compiler
• C# closed-curvature, Heat/geodesic, conformal, and open-boundary smoke runs pass

The standard C++, C#, and WASM GitHub Actions matrices remain the release gate.

Deliberately deferred

True LSCM, harmonic basis generation, ARAP, sparse production-scale constraint elimination, and formal cross-language golden datasets are documented as future work.

[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-04T22:48:04.217718Z	ae20305	PR opened

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