Use Python 3.13 and modern setup-python caching for poetry

Co-authored-by: SupraSummus <[email protected]>

Author: Copilot

.github/workflows/ci.yml

@@ -11,17 +11,15 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Install Poetry
+        run: pipx install poetry
+
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: '3.11'
+          python-version: '3.13'
           cache: 'poetry'
 
-      - name: Install Poetry
-        uses: snok/install-poetry@v1
-        with:
-          virtualenvs-in-project: true
-
       - name: Install dependencies
         run: poetry install