Use Jupyter Book for documentation.

Author: hmgaudecker

.readthedocs.yaml

@@ -1,7 +1,7 @@
 ---
 version: 2
 build:
-  os: ubuntu-lts-latest
+  os: ubuntu-24.04
   tools:
     python: '3.13'
   jobs:
@@ -13,4 +13,9 @@ build:
       - pixi install -e docs
     build:
       html:
-        - pixi run -e docs sphinx-build -T -b html docs/source $READTHEDOCS_OUTPUT/html
+        - pixi run -e docs docs
+    post_build:
+      # Jupyter Book 2.0 builds site content to _build/html.
+      # For ReadTheDocs, we build and then copy to the expected output location.
+      - mkdir --parents $READTHEDOCS_OUTPUT/html/
+      - cp -r docs/source/_build/html/* $READTHEDOCS_OUTPUT/html/

docs/Makefile

@@ -0,0 +1,8 @@
+#!/bin/bash
+set -e
+
+if [ -n "$READTHEDOCS_LANGUAGE" ] && [ -n "$READTHEDOCS_VERSION" ]; then
+    export BASE_URL="/$READTHEDOCS_LANGUAGE/$READTHEDOCS_VERSION"
+fi
+
+jupyter book build --html