Re-enable downgrade tests after PrecompileTools minimum version update

[ChrisRackauckas-Claude]

Summary

The downgrade tests have been temporarily disabled in the Downgrade.yml workflow because they fail when dependencies are downgraded to their minimum compatible versions.

Issue

When Julia downgrades PrecompileTools to v1.0.0 (the minimum compatible version), the package fails to load with the error:

ERROR: LoadError: UndefVarError: `PrecompileTools` not defined

This appears to be an issue with PrecompileTools v1.0.0 not being fully compatible with the current codebase.

Solution Options

1. Bump the minimum PrecompileTools version in the compat section to a version that works correctly
2. Wait for an upstream fix in PrecompileTools

Related

• Disabled in PR that splits JET tests to separate workflow
• Similar to DelayDiffEq.jl#356