Variable dropDuplicateTrianglesConst

dropDuplicateTriangles: Fix = ...

Auto-fix for GEOMETRY_DUPLICATE_INDICES — rewrites geom.indices keeping only the first occurrence of each triangle (canonical key = sorted vertex tuple, so any rotation or winding of the same vertex set collapses).

Doesn't touch vertex arrays — duplicate indices waste traversal / overdraw, not vertex storage. If the dropped triangles' vertices become unreferenced, the matching compactUnusedVertices cleans those up on a separate pass.

Degenerate triangles (any pair of repeated indices) are kept as-is — they're handled by dropDegenerateTriangles.

Idempotent: returns {fixed: false} when no triangle's canonical key is seen twice.