fix: prevent browser freeze when tessellating >50k vertices (#8219 )

[Nixxx19]

Resolves #8219

Changes:

• Added vertex count validation in _processVertices() before calling _tesselateShape() to prevent browser freeze
• Shows friendly warning message when vertex count exceeds 50,000 vertices
• Skips tessellation for large shapes and falls back to TRIANGLE_FAN mode so shapes still render
• Added unit tests to verify warning behavior and normal operation for safe vertex counts

The fix prevents the browser from freezing when libtess tries to tessellate shapes with >65k vertices. The freeze was happening inside libtess during _triangulate(), before any buffer caching logic could run.

Screenshots of the change:

PR Checklist

• npm run lint passes
• [Inline reference] is included / updated (not applicable - this is a bug fix)
• [Unit tests] are included / updated

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Thank You!

[Nixxx19]

@davepagurek @ksen0 whenever you have a chance, could you review this pr? i'd love to hear your feedback.