Add test dependency build step to instantiate test environment

Add a second julia-buildpkg step with project=test to ensure test
dependencies are properly instantiated with SSH authentication before
running tests

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

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

Author: Keno

.github/workflows/CI.yml

@@ -45,6 +45,11 @@ jobs:
       - uses: julia-actions/julia-buildpkg@v1
         with:
           git_cli: true
+      - uses: julia-actions/julia-buildpkg@v1
+        name: Build test dependencies
+        with:
+          project: test
+          git_cli: true
       - uses: julia-actions/julia-runtest@v1
         env:
           JULIA_PKG_USE_CLI_GIT: "true"