Downgrade CI disabled: PrecompileTools v1.0.0 incompatible with Julia 1.10

[ChrisRackauckas-Claude]

Problem

The Downgrade CI job fails because julia-downgrade-compat resolves PrecompileTools to v1.0.0 (the lower bound of compat "1"), which fails to load on Julia 1.10:

ERROR: LoadError: UndefVarError: `PrecompileTools` not defined

This causes all test sets to error since the package itself cannot be precompiled.

Current Workaround

The Downgrade job has been disabled with if: false in #57, following the same pattern as DelayDiffEq.jl.

Potential Fixes

1. Bump PrecompileTools compat lower bound to a version that works correctly on Julia 1.10 (e.g., PrecompileTools = "1.2" or whichever version first supported Julia 1.10 properly)
2. Add PrecompileTools to the skip list in the downgrade workflow: skip: Pkg,TOML,PrecompileTools
3. Investigate PrecompileTools v1.0.0 to determine if this is a bug in that version or an expected incompatibility

References

• PR Refactor CI to use test groups with separate QA environment #57 (CI refactor with test groups)
• DelayDiffEq.jl uses the same if: false pattern for their downgrade job