Optimizing slice allocations using capacity.

Pre-allocating slice capacity prevents expensive memory reallocations and copies during append operations.

When a slice reaches its capacity, Go allocates a new array (usually 2x the size for small slices) and copies elements. If you loop 10,000 times appending to a slice, this reallocation happens roughly 14 times, causing massive CPU and GC overhead. make([]T, length, capacity) eliminates this.