Lagrange Release v6.47.0

Dependencies

• 📌 Update nanobind to 2.13.0.
• 📌 Bump vcpkg baseline and migrate embree3 → embree 4 (v4.4.0): switch to the unified embree port (keeps ray-mask feature), Embree 4 API path by default.
• 📌 Update geogram_delaunay commit reference to 22d84a44d.

Build & CI

• 🏗️ Add vcpkg-registry validation pipeline.
• 🏗️ Fail fast on Windows CRT assertions in test binaries.
• 🏗️ Remove Eigen compile workaround for multi-arch on Xcode 27 Beta 3.
• 🔧 Sync file headers via automated heady update.

Core Module

• 🎨 Refactor weld_indexed_attribute: drop Eigen, ~90% smaller debug, ~34% faster; template on index type only, collapsing the ValueType × Scalar × Index instantiation cross-product (~40 → ~2).
• 🎨 Reduce debug-symbol footprint of transform_mesh.
• 🎨 Add internal::split_edges_only for polygon-preserving edge splits: splits without retriangulating — a split triangle can stay a quad/polygon; interpolates facet/corner attributes.
• 🐛 Fix split_edges interpolation for a vertex on multiple edges.
• 🎨 Add support to only triangulate selected facets in triangulate_polygonal_facets.

IO / FBX

• 🎨 Add embedded texture loading support for FBX: decode raw PNG/JPEG embedded in the FBX via stbi_load_from_memory (previously skipped with a warning).
• 🎨 Add per-facet material_id attribute to scene_to_meshes_and_materials: global scene material index per facet, remapping instance-local ids.
• 🐛 Preserve ufbx face_material as per-facet material_id in FBX loader.

T-Junctions

• ✨ Add resolve_tjunctions mesh-cleanup pass.

Other Modules

• 🎨 PolyDDG: add alignment_lambda (λ_t) tradeoff to compute_smooth_direction_field. (#2033)
• 🐍 Remove __future__ annotation from meshstat script. (#2030)