Module number 

Number type for exact arithmetic

Supports three representations:

• Integer: Arbitrary precision integers (i64 with promotion to BigInt)
• Rational: Exact fractions (numerator/denominator as BigInt)
• Float: Floating-point approximations (f64)

All arithmetic operations use checked arithmetic to detect overflow and automatically promote to BigInt or Rational types when needed. Float operations check for infinity and NaN to prevent silent error propagation.

Enums

Number

Unified number type supporting integers, rationals, and floats