Fix solve!(cache) type instability + JET QA test group#984

ChrisRackauckas merged 6 commits into

SciML:mainSciML/LinearSolve.jl:mainfrom

ChrisRackauckas-Claude:fix-default-solver-type-stabilityChrisRackauckas-Claude/LinearSolve.jl:fix-default-solver-type-stabilityCopy head branch name to clipboard