Writing to a bitmap from multiple threads causes races when writing to bits within the same integer. Instead, write to a separate boolean array while subdividing, then move that to the final mesh bit vector. Notes: - The final copy to the bit vector could be replaced by a generic `copy_from(Span<bool>)` call in the future. - Theoretically we could entirely replace the `BitVector` with an `Array<bool>`, but 1/8 the memory use for edges is likely worth it. Pull Request #105156