ci: ubuntu-24.04 compatibility

ubuntu-24.04 breaks `pip install` for system packages
see also actions/runner-images#10781

action/setup-python would mitigate this effect but runs into different
pip install build issues due to preinstalled sytem packages not found
(i.e. cairo not found)

.github/workflows/run-tests.yml

@@ -26,14 +26,15 @@ jobs:
           - { os: 'windows-latest', python-version: '3.11', inkscape-version: '1.2', continue-on-error: false }
           - { os: 'windows-latest', python-version: '3.10', inkscape-version: '1.1', continue-on-error: false }
           - { os: 'ubuntu-latest', python-version: '3.12', inkscape-version: 'TRUNK', continue-on-error: true }
-          - { os: 'ubuntu-latest', python-version: '3.12', inkscape-version: 'inkex', continue-on-error: false }
+          - { os: 'ubuntu-latest', python-version: 'native', inkscape-version: 'inkex', continue-on-error: false }  # native python to work around https://github.com/actions/runner-images/issues/10781
           - { os: 'ubuntu-latest', python-version: '3.13', inkscape-version: '1.4.0', continue-on-error: false }
 #          - { os: 'ubuntu-latest', python-version: '3.9', inkscape-version: 'inkex==1.0.1', continue-on-error: false }
     continue-on-error: ${{ matrix.continue-on-error }}
 
     steps:
     - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
+      if: ${{ matrix.python-version != 'native' }}
       uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
@@ -53,7 +54,7 @@ jobs:
       if: ${{ matrix.os == 'ubuntu-latest' && startsWith(matrix.inkscape-version, 'inkex') }}
       run: |
         sudo apt-get -y install umockdev libgirepository1.0-dev
-        pip install ${{ matrix.inkscape-version }}
+        pip install --break-system-packages ${{ matrix.inkscape-version }}
     - name: 🍏 install Inkscape
       if: ${{ matrix.os == 'macos-latest' }}
       run: |
@@ -72,7 +73,7 @@ jobs:
         inkscape --version || echo "inkscape not found"
     - name: install requirements
       run: |
-        python -m pip install --upgrade pip
+        python -m pip install --break-system-packages --upgrade pip
         pip install -r requirements.txt
         pip install pytest
     - name: test