lerp static method
Linearly interpolates between two size units.
This creates a smooth transition between different sizing strategies, useful for animations or responsive design.
Implementation
static SizeUnit lerp(SizeUnit a, SizeUnit b, double t) {
if (t <= 0.0) return a;
if (t >= 1.0) return b;
return a * _FixedSize(1.0 - t) + b * _FixedSize(t);
}