Make Enzyme a conditional test dependency loaded only for nopre group

- Remove Enzyme from regular test dependencies in Project.toml
- Add Enzyme as an EXTRA_PKG that's loaded conditionally in runtests.jl
- Only load Enzyme for the nopre group when not on prerelease Julia
- This ensures Enzyme is only loaded when needed and won't cause issues on prerelease

This complements the previous change of moving tests to the nopre group,
ensuring Enzyme is truly optional and only loaded when appropriate.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: ChrisRackauckas

Project.toml

@@ -69,7 +69,6 @@ CommonSolve = "0.2.4"
 ConcreteStructs = "0.2.3"
 DiffEqBase = "6.158.3"
 DifferentiationInterface = "0.6.18, 0.7"
-Enzyme = "0.13.11"
 ExplicitImports = "1.5"
 FastClosures = "0.3.2"
 FastLevenbergMarquardt = "0.1"
@@ -123,7 +122,6 @@ Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
 BandedMatrices = "aae01518-5342-5314-be14-df237901396f"
 BenchmarkTools = "6e4b80f9-dd63-53aa-95a3-0cdb28fa8baf"
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
-Enzyme = "7da242da-08ed-463a-9acd-ee780be4f1d9"
 ExplicitImports = "7d51a73a-1435-4ff3-83d9-f097790105c7"
 FastLevenbergMarquardt = "7a0df574-e128-4d35-8cbd-3d84502bf7ce"
 FixedPointAcceleration = "817d07cb-a79a-5c30-9a31-890123675176"
@@ -170,5 +168,5 @@ path = "lib/NonlinearSolveSpectralMethods"
 path = "lib/SimpleNonlinearSolve"
 
 [targets]
-test = ["Aqua", "BandedMatrices", "BenchmarkTools", "CUDA", "Enzyme", "ExplicitImports", "FastLevenbergMarquardt", "FixedPointAcceleration", "Hwloc", "InteractiveUtils", "LeastSquaresOptim", "LineSearches", "MINPACK", "NLSolvers", "NLsolve", "NaNMath", "NonlinearProblemLibrary", "OrdinaryDiffEqTsit5", "PETSc", "Pkg", "PolyesterForwardDiff", "Random", "ReTestItems", "SIAMFANLEquations", "SparseConnectivityTracer", "SpeedMapping", "StableRNGs", "StaticArrays", "Sundials", "Test", "Zygote"]
+test = ["Aqua", "BandedMatrices", "BenchmarkTools", "CUDA", "ExplicitImports", "FastLevenbergMarquardt", "FixedPointAcceleration", "Hwloc", "InteractiveUtils", "LeastSquaresOptim", "LineSearches", "MINPACK", "NLSolvers", "NLsolve", "NaNMath", "NonlinearProblemLibrary", "OrdinaryDiffEqTsit5", "PETSc", "Pkg", "PolyesterForwardDiff", "Random", "ReTestItems", "SIAMFANLEquations", "SparseConnectivityTracer", "SpeedMapping", "StableRNGs", "StaticArrays", "Sundials", "Test", "Zygote"]
 

test/runtests.jl

@@ -9,6 +9,12 @@ if GROUP == "all" || GROUP == "downstream"
     push!(EXTRA_PKGS, Pkg.PackageSpec("ModelingToolkit"))
     push!(EXTRA_PKGS, Pkg.PackageSpec("SymbolicIndexingInterface"))
 end
+if GROUP == "all" || GROUP == "nopre"
+    # Only add Enzyme for nopre group if not on prerelease Julia
+    if isempty(VERSION.prerelease)
+        push!(EXTRA_PKGS, Pkg.PackageSpec("Enzyme"))
+    end
+end
 length(EXTRA_PKGS) ≥ 1 && Pkg.add(EXTRA_PKGS)
 
 const RETESTITEMS_NWORKERS = parse(