isWithinTolerance method
Checks if this BigInt is within a fixed tolerance of the target value.
Formula: (this - target).abs() <= tolerance.
Assumes tolerance is a non-negative BigInt.
Implementation
bool isWithinTolerance(BigInt target, BigInt tolerance) {
assert(!tolerance.isNegative, 'Tolerance cannot be negative');
return (this - target).abs() <= tolerance;
}