Add --round-leaves option to auto-pad leaf count to nearest arity^n

[carpalsgrabby]

Summary

Sometimes users want to know the nearest valid full-tree leaf count without manually calculating it. The script computes fullLeaves, but doesn’t provide an option to round the user’s input automatically.

Proposal

• Add --round-leaves flag.
• Instead of requiring user input for leaves, compute:
  • rounded_up = arity**ceil(log(leaves, arity))
  • rounded_down = arity**floor(log(leaves, arity))
• Print both possibilities.

Benefit

Useful for designing commitment systems or memory layouts that must align to exact powers of arity.