ci: Use Python 3.13

- Newest Linux/macOS/Windows environments (should be roughly same as release,
  especially for Windows/macOS)
- Nightly binary builds
- Release automation

Closes #8205

.github/workflows/ci.yml

@@ -189,20 +189,24 @@ jobs:
           - testenv: py312-pyqt67
             os: ubuntu-22.04
             python: "3.12"
+          ### PyQt 6.7 (Python 3.13, placeholder for PyQt 6.8)
+          - testenv: py313-pyqt67
+            os: ubuntu-22.04
+            python: "3.13"
           ### macOS Ventura
           - testenv: py312-pyqt67
             os: macos-13
-            python: "3.12"
+            python: "3.13"
             args: "tests/unit"  # Only run unit tests on macOS
           ### macOS Sonoma (M1 runner)
           - testenv: py312-pyqt67
             os: macos-14
-            python: "3.12"
+            python: "3.13"
             args: "tests/unit"  # Only run unit tests on macOS
           ### Windows
           - testenv: py312-pyqt67
             os: windows-2019
-            python: "3.12"
+            python: "3.13"
     runs-on: "${{ matrix.os }}"
     steps:
       - uses: actions/checkout@v4

.github/workflows/nightly.yml

@@ -43,7 +43,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.12"
+          python-version: "3.13"
       - name: Install dependencies
         run: |
             python -m pip install -U pip

.github/workflows/release.yml

@@ -16,13 +16,14 @@ on:
       python_version:
         description: 'Python version'
         required: true
-        default: '3.12'
+        default: '3.13'
         type: choice
         options:
           - '3.9'
           - '3.10'
           - '3.11'
           - '3.12'
+          - '3.13'
 jobs:
   prepare:
     runs-on: ubuntu-20.04