v3.84.0

LinearSolve v3.84.0

Diff since v3.83.0

Merged pull requests:

• ci: uniformize onto centralized CI (project-model SublibraryCI + cleanup) (#1006) (@ChrisRackauckas-Claude)
• Add SparseColumnPivotedQR (CSC-native) as default sparse QR + KLU singular fallback + adjoint path (#1007) (@ChrisRackauckas-Claude)
• Guard KLU/PureKLU solve! against non-finite (masked-singular) results (#1009) (@ChrisRackauckas-Claude)