Fix Gitea Actions: drop custom job container, use setup-python

The python:3.11-slim job container lacked a Node.js runtime, so the
runner couldn't exec actions/checkout inside it. Run jobs on the
default runner image instead and pin Python via actions/setup-python.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -8,70 +8,65 @@ jobs:
   lint:
     name: lint:ruff
     runs-on: ubuntu-latest
-    container: python:3.11-slim
     steps:
       - uses: actions/checkout@v4
-      - name: Cache pip
-        uses: actions/cache@v4
+      - uses: actions/setup-python@v5
         with:
-          path: ~/.cache/pip
-          key: pip-${{ hashFiles('pyproject.toml') }}
+          python-version: "3.11"
+          cache: pip
+          cache-dependency-path: pyproject.toml
       - run: pip install -e ".[dev,plotting]"
       - run: ruff check gallery plotstyle tests
 
   format:
     name: format:ruff
     runs-on: ubuntu-latest
-    container: python:3.11-slim
     steps:
       - uses: actions/checkout@v4
-      - name: Cache pip
-        uses: actions/cache@v4
+      - uses: actions/setup-python@v5
         with:
-          path: ~/.cache/pip
-          key: pip-${{ hashFiles('pyproject.toml') }}
+          python-version: "3.11"
+          cache: pip
+          cache-dependency-path: pyproject.toml
       - run: pip install -e ".[dev,plotting]"
       - run: ruff format --check gallery plotstyle tests
 
   typecheck:
     name: typecheck:ty
     runs-on: ubuntu-latest
-    container: python:3.11-slim
     steps:
       - uses: actions/checkout@v4
-      - name: Cache pip
-        uses: actions/cache@v4
+      - uses: actions/setup-python@v5
         with:
-          path: ~/.cache/pip
-          key: pip-${{ hashFiles('pyproject.toml') }}
+          python-version: "3.11"
+          cache: pip
+          cache-dependency-path: pyproject.toml
       - run: pip install -e ".[dev,plotting]"
       - run: ty check gallery plotstyle
 
   vulnerabilities:
     name: vulnerabilities:pip-audit
     runs-on: ubuntu-latest
-    container: python:3.11-slim
     steps:
       - uses: actions/checkout@v4
-      - name: Cache pip
-        uses: actions/cache@v4
+      - uses: actions/setup-python@v5
         with:
-          path: ~/.cache/pip
-          key: pip-${{ hashFiles('pyproject.toml') }}
+          python-version: "3.11"
+          cache: pip
+          cache-dependency-path: pyproject.toml
       - run: pip install -e ".[dev,plotting]"
       - run: pip-audit
 
   test:
     name: test:pytest
     runs-on: ubuntu-latest
-    container: python:3.11-slim
     needs: [lint, format, typecheck, vulnerabilities]
     steps:
       - uses: actions/checkout@v4
-      - name: Cache pip
-        uses: actions/cache@v4
+      - uses: actions/setup-python@v5
         with:
-          path: ~/.cache/pip
-          key: pip-${{ hashFiles('pyproject.toml') }}
+          python-version: "3.11"
+          cache: pip
+          cache-dependency-path: pyproject.toml
       - run: pip install -e ".[dev,plotting]"
       - run: python -m pytest tests/ -v