Imports

Section 28.3 - Symmetric positive-definite matrices and least-squares approximation (legacy compatibility path)

Third-edition-numbered compatibility path for symmetric positive-definite matrices and least-squares approximation. The canonical fourth-edition source is CLRSLean.FourthEdition.Chapter_28.Section_28_3_Symmetric_Positive_Definite; this module forwards to it so legacy imports keep working during the compatibility period (see docs/migrations/clrs4.md).