docs: switch from mkdocs to properdocs (#2946)

properdocs is a drop-in MkDocs fork by the original MkDocs maintainers.
The existing plugins (include-markdown, macros, intersphinx) and pymdown
extensions work unchanged; themes are unbundled, so the readthedocs
theme comes from properdocs-theme-readthedocs.

Assisted-by: ClaudeCode:claude-fable-5

.github/workflows/test.yml

@@ -23,7 +23,7 @@ on:
       - .travis.yml
       - README.md
       - azure-pipelines.yml
-      - mkdocs.yml
+      - properdocs.yml
       - noxfile.py
   workflow_dispatch:
     # allow manual runs on branches without a PR

.readthedocs.yml

@@ -8,4 +8,4 @@ build:
     - asdf plugin add uv
     - asdf install uv latest
     - asdf global uv latest
-    - NO_COLOR=1 uv run --python 3.14 --managed-python --no-dev --group docs mkdocs build --strict --site-dir $READTHEDOCS_OUTPUT/html
+    - NO_COLOR=1 uv run --python 3.14 --managed-python --no-dev --group docs properdocs build --strict --site-dir $READTHEDOCS_OUTPUT/html

AGENTS.md

@@ -11,7 +11,7 @@
 - `nox -s tests -- test -k before_build` — single integration test/file via pytest `-k`.
 - `nox -s lint` — run all linters (pre-commit/prek).
 - `nox -s pylint` — run pylint separately (not in pre-commit).
-- `nox -s docs` — mkdocs serve (interactive) or build (non-interactive).
+- `nox -s docs` — properdocs serve (interactive) or build (non-interactive).
 - Set up local dev env at `.venv`: `uv sync` (dependency groups used).
 
 ## Project layout
@@ -19,7 +19,7 @@
 - `test/` — **integration tests** (expensive, run actual wheel builds).
 - `unit_test/` — **unit tests** (fast, no wheel builds).
 - `bin/` — maintainer scripts (update pins, generate README tables, schema, etc.).
-- `docs/` — mkdocs source.
+- `docs/` — properdocs (MkDocs fork) source.
 
 ## Testing specifics
 - Three test suites exist, run in this order by `bin/run_tests.py`:

azure-pipelines.yml

@@ -12,7 +12,7 @@ pr:
       - .readthedocs.yml
       - .travis.yml
       - README.md
-      - mkdocs.yml
+      - properdocs.yml
       - noxfile.py
 
 jobs:

noxfile.py

@@ -228,7 +228,9 @@ def docs(session: nox.Session) -> None:
     """
     pyproject = nox.project.load_toml()
     session.install("-e.", *nox.project.dependency_groups(pyproject, "docs"))
-    session.run("mkdocs", "serve" if session.interactive else "build", "--strict", *session.posargs)
+    session.run(
+        "properdocs", "serve" if session.interactive else "build", "--strict", *session.posargs
+    )
 
 
 @nox.session(default=False)

pyproject.toml

@@ -68,7 +68,8 @@ docs = [
     "mkdocs-include-markdown-plugin==7.1.8",
     "mkdocs-intersphinx>=0.1.1; python_version >= '3.12'",
     "mkdocs-macros-plugin>=1.4.1",
-    "mkdocs==1.6.1",
+    "properdocs==1.6.7",
+    "properdocs-theme-readthedocs",
     "pymdown-extensions",
     "rich",
 ]