QA: Aqua/JET findings marked @test_broken pending fix

[ChrisRackauckas-Claude]

The QA test group (Aqua + JET) surfaces two genuine findings. To keep the QA CI group green while these are tracked, both are marked @test_broken in test/qa/qa.jl (the passing Aqua sub-checks remain enabled via Aqua.test_all(...; deps_compat=false)). These should be fixed and un-broken.

1. Aqua deps_compat (extras) — missing compat entry for Pkg

Aqua.test_deps_compat fails because the package declares Pkg in [extras] / [targets].test but has no [compat] entry for it:

Base.PkgId(... "SparseColumnPivotedQR") does not declare a compat entry for the following extras:
 Pkg [44cfe95a-1eb2-52ea-b672-e2afdf69b78f]

Fix: add a Pkg compat entry to the main Project.toml [compat] section (e.g. Pkg = "1"), or drop the Pkg extra/target if it is no longer used by the test suite. (Note: a compat fix here is a real change to the root Project.toml, so it was intentionally NOT applied as part of the QA-green pass — it is left for a dedicated fix.)

2. JET report_package — 4 no matching method errors in Base.:\\

JET.test_package(SparseColumnPivotedQR; target_defined_modules = true) reports 4 possible errors, all in the \ solve paths in src/SparseColumnPivotedQR.jl:

┌ \(F::SparseColumnPivotedQRFactorization{…}, b::AbstractVector{…}) @ src/SparseColumnPivotedQR.jl:2392
│ no matching method found `ldiv!(::Matrix{Float64}, ::SparseColumnPivotedQRFactorization, ::AbstractVector)` (1/2 union split)
┌ \(F::SparseColumnPivotedQRFactorization{…}, b::AbstractVector) @ src/SparseColumnPivotedQR.jl:2399
│ no matching method found `ldiv!(::Matrix{Float64}, ::SparseColumnPivotedQRFactorization, ::AbstractVector)` (1/2 union split)
┌ \(aF::Adjoint{…}, b::AbstractVector{…}) @ src/SparseColumnPivotedQR.jl:2532
│ no matching method found `_ldiv_adjoint!(::Matrix{Float64}, ::SparseColumnPivotedQRFactorization, ::AbstractVector)` (1/2 union split)
┌ \(aF::Adjoint{…}, b::AbstractVector) @ src/SparseColumnPivotedQR.jl:2538
│ no matching method found `_ldiv_adjoint!(::Matrix{Float64}, ::SparseColumnPivotedQRFactorization, ::AbstractVector)` (1/2 union split)

The \ methods allocate x = zeros(T, F.n) and call ldiv!(x, F, b) / _ldiv_adjoint!(x, ..., b). JET's union-split sees a branch where x is inferred as Matrix{Float64} (rather than Vector), for which no ldiv!/_ldiv_adjoint! method matches. Fix: either tighten the ldiv!/_ldiv_adjoint! signatures / the inferred type of x, or add the missing AbstractMatrix/AbstractVecOrMat method, so JET infers a matching method on every branch.

These are currently @test_broken false in test/qa/qa.jl so the QA CI group is green; please fix and remove the broken markers.

Ignore until reviewed by @ChrisRackauckas.

[ChrisRackauckas-Claude]

Status update from #50 (run_qa v1.6 + ExplicitImports conversion):

• Item 1 (Aqua deps_compat, missing Pkg compat) — RESOLVED. The Pkg extra that triggered this was dropped during the folder-model conversion (Use SciMLTesting v1.2 (folder-based run_tests) #45), so Aqua.test_all now runs all sub-checks green with no deps_compat=false disable. The broken marker for this item is removed in QA: run_qa v1.6 form + ExplicitImports #50.

• Item 2 (JET 4 union-split no matching method on the \ solve paths) — still open. QA: run_qa v1.6 form + ExplicitImports #50 carries it forward as jet_broken = true (report_package + @test_broken isempty(get_reports)), so the QA group stays green while the finding stands. This issue remains the tracking link for item 2; please close it once the \ x = zeros(T, F.n) inference is fixed so JET reports clean.