Fix CI: use shell steps instead of JS actions (Alpine runner has no node)

.gitea/workflows/ci.yml

@@ -10,24 +10,27 @@ jobs:
   checks:
     runs-on: docker
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      - name: Install Python and tools
+        run: |
+          apk add --no-cache python3 py3-pip git
 
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
+      - name: Checkout
+        run: |
+          git init -q
+          git remote add origin "${GITHUB_SERVER_URL:-http://10.8.0.52:8080}/$GITHUB_REPOSITORY.git"
+          git fetch -q --depth 1 origin "$GITHUB_SHA"
+          git checkout -q FETCH_HEAD
 
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip
-          python -m pip install -e ".[dev]"
+          python3 -m pip install --upgrade pip
+          python3 -m pip install -e ".[dev]"
 
       - name: Lint (ruff)
-        run: ruff check src tests
+        run: python3 -m ruff check src tests
 
       - name: Typecheck (mypy)
-        run: mypy src
+        run: python3 -m mypy src
 
       - name: Tests (pytest + coverage)
-        run: python -m pytest -v --cov=selectel_ml_tui --cov-report=term-missing
+        run: python3 -m pytest -v --cov=selectel_ml_tui --cov-report=term-missing