Chapter 7 - Quicksort

This legacy guide forwards to the native fourth-edition Chapter 7 guide CLRSLean.FourthEdition.Chapter_07. The third-edition-numbered section imports CLRSLean.Chapter_07.Section_07_* (including the comparison- probability submodule) also forward to the native fourth-edition sources during the compatibility period (see docs/migrations/clrs4.md).