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