Fix CI: install sbt before running tests

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: MateuszKubuszok

.github/workflows/ci.yml

@@ -47,5 +47,11 @@ jobs:
           distribution: temurin
           java-version: 17
           cache: sbt
+      - name: Install sbt
+        run: |
+          echo "deb https://repo.scala-sbt.org/scalasbt/debian all main" | sudo tee /etc/apt/sources.list.d/sbt.list
+          curl -sL "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x2EE0EA64E40A89B84B2DF73499E82A75642AC823" | sudo apt-key add
+          sudo apt-get update
+          sudo apt-get install -y sbt
       - name: Run tests
         run: sbt "++${{ matrix.scala }}; tests/test"