🔧 MAINTAIN: Add pre-commit and mypy tox envs, fix docs builder command

Co-authored-by: chrisjsewell <2997570+chrisjsewell@users.noreply.github.com>

Author: Copilot

AGENTS.md

@@ -102,14 +102,23 @@ tox -e docs-clean
 # Build docs (incremental)
 tox -e docs-update
 
-# Build with a specific builder (e.g., linkcheck)
-BUILDER=linkcheck tox -e docs-update
+# Build with a specific builder (e.g., linkcheck to validate external links)
+tox -e docs-update -- linkcheck
 ```
 
 ### Code Quality
 
 ```bash
-# Run pre-commit hooks on all files
+# Run all pre-commit hooks (ruff, mypy, trailing whitespace, etc.)
+tox -e pre-commit
+
+# Run pre-commit with specific hook
+tox -e pre-commit -- --all-files ruff
+
+# Run mypy type checking
+tox -e mypy
+
+# Run pre-commit hooks directly (if pre-commit is installed)
 pre-commit run --all-files
 ```
 

tox.ini

@@ -19,3 +19,11 @@ allowlist_externals = rm
 commands =
     clean: rm -rf docs/_build
     sphinx-build -nW --keep-going -b {posargs:html} docs/ docs/_build/{posargs:html}
+
+[testenv:pre-commit]
+deps = pre-commit
+commands = pre-commit run {posargs:--all-files}
+
+[testenv:mypy]
+deps = mypy
+commands = mypy mdit_py_plugins {posargs}