Docs: Add contributing guide

CONTRIBUTING.md

@@ -0,0 +1,95 @@
+# Contributing to CADET-RDM
+
+This file covers the mechanics of working on CADET-RDM: development setup, tests, documentation, and releases.
+For what the project is and where it is going, see [PROJECT.md](PROJECT.md).
+For user-facing installation and usage, see https://cadet-rdm.readthedocs.io.
+
+
+## Development setup
+
+Clone the repository and install it in editable mode together with the testing dependencies:
+
+```bash
+git clone git@github.com:cadet/CADET-RDM.git
+cd CADET-RDM
+pip install -e . --group testing
+```
+
+The `--group` flag requires pip 25.1 or newer.
+A dedicated conda or virtual environment is strongly recommended, since CADET-RDM inspects the active environment when recording run metadata.
+
+Two things outside the Python environment are required before the test suite will pass.
+
+Git LFS must be installed and initialized (`git lfs install`), because CADET-RDM tracks common data filetypes through LFS.
+Installation instructions per platform are in the [user documentation](https://cadet-rdm.readthedocs.io/en/latest/user_guide/installation.html).
+
+Git needs a global identity, because the tests create repositories and commit to them:
+
+```bash
+git config --global user.name "Your Name"
+git config --global user.email "you@example.com"
+```
+
+
+## Tests
+
+The suite lives in `tests/` and runs under pytest.
+Tests create real Git repositories in temporary directories, so they are slower and more side-effect-heavy than pure unit tests.
+
+Four markers are defined in `pyproject.toml`:
+
+- `slow` for long-running tests,
+- `server_api` for tests that talk to the GitLab or GitHub API,
+- `container` for tests that require Docker, Podman, or Apptainer,
+- unmarked tests, which need nothing beyond a local Git installation.
+
+CI runs only the unmarked subset:
+
+```bash
+pytest tests -m "not server_api and not container and not slow"
+```
+
+Run that selection locally before opening a pull request.
+The marked subsets require credentials or a container runtime and are expected to be run deliberately, not by default.
+
+Tests are executed on Ubuntu against Python 3.11, 3.12, and 3.13, plus one Windows and one macOS job on 3.13.
+The minimum supported Python version is 3.11.
+
+
+## Documentation
+
+The documentation source is Sphinx with MyST markdown under `docs/source`, published to Read the Docs.
+
+```bash
+pip install -e . --group docs
+cd docs
+sphinx-build -b html source build
+```
+
+The rendered output is in `docs/build` and can be opened in any browser.
+User-facing behavior changes should be reflected in `docs/source/user_guide` in the same pull request that changes the behavior.
+
+
+## Branches and pull requests
+
+Work happens on feature branches that are opened as pull requests.
+CI runs the test stage on pull requests against any branch, and on pushes to `main` and `dev`.
+
+Until its fate is settled, base new work on `main` and ask if in doubt.
+
+Commit subjects are short and imperative, optionally prefixed with the area of the change (`Docs:`, `Fix:`, `Feat:`, `Tests:`, `CI:`).
+The subject says what changed; the body, where one is needed, says why.
+
+
+## Releases
+
+Releases are published to PyPI from GitHub.
+
+1. Bump `__version__` in `cadetrdm/__init__.py`.
+   The package version is read from that attribute, so it is the single source of truth.
+2. Update `.zenodo.json` if authorship or metadata changed.
+3. Commit, tag as `vX.Y.Z`, and push the tag.
+4. Publish a GitHub release for the tag.
+
+Publishing the release triggers `.github/workflows/release.yml`, which builds the distributions and uploads them to PyPI through trusted publishing.
+The workflow deliberately triggers on published releases rather than on tags, to avoid running twice for a single release.

README.md

@@ -3,7 +3,7 @@
 [![CI](https://github.com/cadet/CADET-RDM/actions/workflows/CI.yml/badge.svg)](https://github.com/cadet/CADET-RDM/actions/workflows/CI.yml)
 [![Documentation](https://readthedocs.org/projects/cadet-rdm/badge/?version=latest)](https://cadet-rdm.readthedocs.io)
 [![License](https://img.shields.io/github/license/cadet/cadet-rdm)](LICENSE)
-[![Python](https://img.shields.io/badge/python-3.9%2B-blue)](https://www.python.org/)
+[![Python](https://img.shields.io/badge/python-3.11%2B-blue)](https://www.python.org/)
 
 CADET-RDM is a Research Data Management toolbox developed at Forschungszentrum Jülich.
 It supports computational research projects by tracking code, data, environments, and generated results in a reproducible and shareable way.
@@ -89,4 +89,5 @@ It includes installation instructions, usage guides for the different interfaces
 ## Project information
 
 - **License:** see [LICENSE](LICENSE)
-- **Authors and contributors:** see [AUTHORS](AUTHORS.md)
+- **Contributing:** see [CONTRIBUTING](CONTRIBUTING.md)
+- **Authors and contributors:** see [AUTHORS](AUTHORS.md)

docs/source/index.md

@@ -1,4 +1,4 @@
-```{include} ./user_guide/introduction.md
+```{include} ../../README.md
 ```
 
 ```{toctree}