fix: drop container job — actions/checkout needs node on runner

python:3.13-slim lacks node, which actions/checkout@v4 requires.
Run test job on bare runner with setup-python instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -7,10 +7,11 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
-    container:
-      image: python:3.13-slim
     steps:
       - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.13'
       - run: pip install pyyaml ruff pytest
       - run: ruff check src/ tests/
       - run: PYTHONPATH=src pytest tests/ -v