build: upgrade Sphinx 4→7, drop m2r2/recommonmark, Python 3.11+

.github/workflows/build.yml

@@ -10,14 +10,14 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
       with:
           submodules: recursive
 
     - name: Set up Python
-      uses: actions/setup-python@v1
+      uses: actions/setup-python@v5
       with:
-        python-version: 3.12
+        python-version: "3.13"
     - name: Install APT dependencies
       run: |
         sudo apt-get install -y git build-essential apt-utils wget libfreetype6 libpng-dev libopenblas-dev gcc gfortran libsnappy-dev graphviz

.readthedocs.yml

@@ -8,7 +8,7 @@ version: 2
 build:
   os: ubuntu-22.04
   tools:
-    python: "3.11"
+    python: "3.13"
   jobs:
     post_create_environment:
       - pip install poetry