Raise KernelAbstractions and MuladdMacro downgrade floors to fix CPU downgrade resolution

[ChrisRackauckas-Claude]

Ignore until reviewed by @ChrisRackauckas.

Problem

The test (alldeps, lts, CPU) / Downgrade Tests - CPU master lane is RED. It fails at the Pkg.test sandbox resolution stage (before any test runs) with:

ERROR: LoadError: Unsatisfiable requirements detected for package PrettyTables [08abe8d2]:
 ...
 ├─restricted by compatibility requirements with CUDA [052768ef] to versions: 2.0.0-2.4.0
 └─restricted by compatibility requirements with SymbolicIndexingInterface ... to versions: 3.0.0-3.3.2 — no versions left

Root cause

The downgrade resolver (julia-downgrade-compat@v2 + Resolver.jl --min=@deps) pins the root deps to their minimal versions. At Pkg.test sandbox-resolution time (allow_reresolve=false), those pinned floors — Adapt 4.3.0, KernelAbstractions 0.9.36, LinearSolve 3.75.0, RecursiveArrayTools 4.0.0, EnzymeCore 0.8.20 — constrain CUDA (a test-only dep) into the range 5.5.1–5.8.2. Every CUDA in that range requires PrettyTables 2.x, while the rest of the SciML test stack pulls in PrettyTables 3.x → empty intersection.

CUDA 5.9.0 is the minimal CUDA that uses PrettyTables 3, but it requires KernelAbstractions ≥ 0.9.38. The floor KernelAbstractions = "0.9" minimal-resolves to 0.9.36, which caps CUDA at ≤ 5.8.2.

Bumping KernelAbstractions to 0.9.38 lets CUDA resolve to 5.9.0 (PrettyTables 3) and uncovered a second stale floor: StochasticDiffEq 7 pulls in StochasticDiffEqHighOrder 2, which requires MuladdMacro ≥ 0.2.4, but the floor MuladdMacro = "0.2" minimal-resolves to 0.2.1.

Fix

• KernelAbstractions: 0.9 → 0.9.38 (root + test/Project.toml) — the minimum CUDA 5.9.0 needs.
• MuladdMacro: 0.2 → 0.2.4 (root) — the minimum StochasticDiffEqHighOrder needs (also the latest 0.2.x).

Both are the exact registry minimums; no upper bounds touched.

Verification (local, Julia 1.10 / lts)

Reproduced the exact CI failure, then with the floor bumps:

• Real julia-downgrade-compat@v2 + Resolver.jl --min=@deps resolution succeeds.
• Pkg.test(; force_latest_compatible_version=false, allow_reresolve=false) sandbox resolves to CUDA v5.9.0, PrettyTables v3.3.2, KernelAbstractions v0.9.38, MuladdMacro v0.2.4, StochasticDiffEq v7.0.0.
• The full GROUP=CPU test suite runs and passes on the downgraded environment (Pkg.test exit 0, "DiffEqGPU tests passed", zero failures/errors).

🤖 Generated with Claude Code