Add benchmarks for large leaf counts and arity values

[carpalsgrabby]

Summary

The script may be used with very large values (up to 2³² or more). Performance benchmarking would help track how long exponentiation and math operations take as inputs grow.

Proposal

• Add benchmarks/ folder using pytest-benchmark or a custom timer.
• Benchmark:
  • compute_layout() with large leaves (10^6–10^12)
  • different arities (2, 4, 8, 16, 32)

Benefit

Provides insight into scaling and potential optimizations.