Imports

Section 25.1 - All-pairs shortest paths model (legacy compatibility path)

Third-edition-numbered compatibility path for the all-pairs shortest-paths model. The canonical fourth-edition source is CLRSLean.FourthEdition.Chapter_23.Section_23_1_All_Pairs_Model; this module forwards to it so legacy imports keep working during the compatibility period (see docs/migrations/clrs4.md).