Skill: BigUnit for precision arithmetic guidance

[bazmatic]

Summary

Adds a new skill that guides Claude when working with the BigUnit TypeScript library — a zero-dependency bigint-based library for precise arithmetic with numbers of varying precision. This is particularly useful for cryptocurrency token amounts (ETH 18 decimals, USDC 6 decimals) and financial calculations where floating-point errors are unacceptable.

Full disclosure: I authored this in my own time for a previous crypto-exchange project. It is battle-tested. It is a very useful library and can hugely simplify working with token values.

Changes

• skills/bigunit/SKILL.md (new, 175 lines) — Complete reference covering:
  • Core concepts (internal bigint representation, precision propagation)
  • Creating values via BigUnit.from(), specific constructors, and BigUnitFactory
  • Arithmetic, comparisons, output formatting, and precision conversion
  • Common pitfalls (missing precision on bigint, unexpected result precision, truncation vs rounding, float issues)
  • Typical patterns for token conversion, fee calculation, splitting, and markup removal

Technical Details

The skill triggers when code involves BigUnit, BigUnitFactory, BigUnitish, asPrecision(), imports from 'bigunit', or precision-sensitive financial/crypto arithmetic.