Updated simplification algorithm

[HeDo88TH]

• Updated simplification algorithm
• Refactored options
• Cleanup dead code

Fixes #23

[Copilot]

Pull request overview

Updates the mesh decimation stage to address issue #23 (later LODs not further reducing) by refactoring how simplification parameters are passed into MeshDecimatorCore, while also removing unused vertex-attribute code paths.

Changes:

• Replace legacy decimator flags with a new SimplificationOptions configuration object passed from DecimationStage.
• Modify FastQuadricMeshSimplification to use Options, add curvature-weighted error, and change attribute blending behavior.
• Remove dead code for tangents/bone weights in MeshDecimatorCore.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
Obj2Tiles/Stages/DecimationStage.cs	Switches decimation setup to SimplificationOptions and adds a warning when reduction is minimal.
MeshDecimatorCore/SimplificationOptions.cs	Introduces a new options struct to configure simplification behavior.
MeshDecimatorCore/Algorithms/DecimationAlgorithm.cs	Replaces PreserveBorders with an Options property to carry simplification settings.
MeshDecimatorCore/Algorithms/FastQuadricMeshSimplification.cs	Refactors algorithm behavior to read from Options, adds curvature handling, and changes vertex attribute interpolation strategy.
MeshDecimatorCore/Mesh.cs	Removes tangents/bone-weight support and related recalculation logic.
MeshDecimatorCore/BoneWeight.cs	Removes unused bone-weight type as part of dead-code cleanup.