✨ feat(playbook): add plan progress tracking and rules updates

CONTRIBUTING.md

@@ -1,7 +1,34 @@
-# Contributing
+# Contributing
+
+Thanks for improving the Playbook templates and tooling. This repo is a template
+source for downstream projects, so changes should stay small, predictable, and
+backwards compatible when possible.
+
+## What to change
+
+- Templates: `templates/`, `rulesets/`, `docs/`
+- Tooling: `scripts/`
+- Tests: `tests/`
 
 ## Commit messages
 
-Follow the repository commit message standard:
+Follow `docs/common/commit_message.md` and use the required emoji/type mapping.
 
-- `docs/common/commit_message.md`
+## Tests
+
+Run the relevant checks before pushing:
+
+```bash
+python -m unittest discover -s tests/cli -v
+python -m unittest discover -s tests -p "test_*.py" -v
+sh tests/templates/validate_python_templates.sh
+sh tests/templates/validate_cpp_templates.sh
+sh tests/templates/validate_ci_templates.sh
+sh tests/templates/validate_project_templates.sh
+sh tests/integration/check_doc_links.sh
+```
+
+## Templates and docs
+
+- Keep placeholder definitions documented in `templates/README.md`.
+- Update template last-updated dates when changing template content.