use Python 3.13 to build docs with Sphinx 9

Author: zacharyburnett

.readthedocs.yaml

@@ -17,14 +17,22 @@ formats:
   - pdf
 
 build:
-  os: ubuntu-22.04
+  os: ubuntu-24.04
   tools:
-    python: mambaforge-4.10
+    python: mambaforge-latest
+  jobs:
+    post_checkout:
+      - git fetch --unshallow || true
+      - git config remote.origin.fetch '+refs/heads/*:refs/remotes/origin/*' || true
+      - git fetch --all --tags || true
+    pre_install:
+      - git update-index --assume-unchanged docs/rtd_environment.yaml docs/conf.py
+    post_install:
+      - git describe --exact-match || towncrier build --keep
 
 conda:
   environment: docs/rtd_environment.yaml
 
-# Optionally set the version of Python and requirements required to build your docs
 python:
   install:
     - method: pip

docs/rtd_environment.yaml

@@ -1,8 +1,6 @@
-name: rtd311
 channels:
   - conda-forge
-  - defaults
 dependencies:
-  - python=3.11
+  - python=3.13
   - pip
   - graphviz