Fix downgrade.yml workflow: add missing version arguments (#47)

* Fix downgrade.yml workflow: add missing version arguments

The downgrade workflow requires:
- `version` argument in setup-julia step
- `julia_version` argument in julia-downgrade-compat action

Without these, the workflow may fail or use incorrect Julia versions.

This PR ensures both arguments are properly specified to match the
matrix version.

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* fixup

---------

Co-authored-by: Stefan Krastanov <stefan@krastanov.org>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>
Co-authored-by: Stefan Krastanov <github.acc@krastanov.org>

Author: 3 people

.github/workflows/downgrade.yml

@@ -24,6 +24,7 @@ jobs:
       - uses: julia-actions/julia-downgrade-compat@v2
         with:
           skip: Pkg,TOML,InteractiveUtils,Random,LinearAlgebra,Dates
+          julia_version: ${{ matrix.version }}
       - uses: julia-actions/cache@v2
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1