Swap optimization

In exchange sorts, an optimization should be introduced to avoid swaps where both elements are the same. This can happen, for instance, in quicksort.

Start by locating the exchange-sort implementations and the swap logic used by quicksort. Check how equal elements are handled, then verify that equal-value swaps are avoided without changing sorting behavior; the issue names no tests, so use the existing sorting checks if available.

Written by the indexing model from the issue text.