py(deps[dev]): add types-docutils stubs and project config for sphinx_pytest_fixtures

why: The new sphinx_pytest_fixtures extension uses docutils node types
that need type stubs for mypy, and its integration tests use a custom
pytest marker.
what:
- Add types-docutils to dev dependencies in pyproject.toml
- Add mypy override to ignore missing imports for sphinx_pytest_fixtures
  and sphinx_pytest_fixtures.* (extension lives under docs/_ext, outside
  the mypy src/tests search path)
- Register "integration" pytest marker for sphinx integration tests
- Update uv.lock with types-docutils resolution

Author: tony

pyproject.toml

@@ -79,6 +79,7 @@ dev = [
   # Lint
   "ruff",
   "mypy",
+  "types-docutils",  # stubs for docutils used by sphinx_pytest_fixtures
 ]
 
 docs = [
@@ -133,6 +134,10 @@ files = [
 module = ["sphinx_fonts"]
 ignore_missing_imports = true
 
+[[tool.mypy.overrides]]
+module = ["sphinx_pytest_fixtures", "sphinx_pytest_fixtures.*"]
+ignore_missing_imports = true
+
 [tool.coverage.run]
 branch = true
 parallel = true
@@ -241,6 +246,9 @@ testpaths = [
   "docs",
   "README.md",
 ]
+markers = [
+  "integration: sphinx integration tests (require full sphinx build)",
+]
 filterwarnings = [
   "ignore:The frontend.Option(Parser)? class.*:DeprecationWarning::",
   "ignore::DeprecationWarning:libtmux.*:",