Enhance contributing.md with development workflow

Added comprehensive sections:
- Development Setup: Prerequisites, quick start, running tests
- Code Quality: Commands for check, typecheck, format
- Building Documentation: Commands for docs and link checking
- Pull Request Guidelines: Before submitting checklist, commit
  message standards (no AI mentions), submission workflow

Expanded from 17 to 103 lines with actionable guidance.

Author: jensens

docs/source/contributing.md

@@ -4,9 +4,95 @@
 
 The sources are in a GIT DVCS with its main branches at [Github](https://github.com/mxstack/mxmake).
 
+## Development Setup
+
+### Prerequisites
+
+- Python 3.9 or later
+- Git
+- make
+
+### Quick Start
+
+Clone the repository and set up the development environment:
+
+```bash
+git checkout https://github.com/mxstack/mxmake.git
+cd mxmake
+make install
+```
+
+This will:
+- Create a virtual environment (`.venv`)
+- Install mxmake in development mode
+- Install all development dependencies
+
+### Running Tests
+
+```bash
+make test           # Run all tests
+make coverage       # Run tests with coverage report
+```
+
+### Code Quality
+
+```bash
+make check          # Run all QA checks (ruff, isort)
+make typecheck      # Run type checking (mypy)
+make format         # Auto-format code
+```
+
+### Building Documentation
+
+```bash
+make docs              # Build Sphinx documentation
+make docs-linkcheck    # Check for broken links in docs
+```
+
+Documentation will be built in `docs/build/html/`.
+
+## Pull Request Guidelines
+
+### Before Submitting
+
+1. **Run tests**: Ensure all tests pass with `make test`
+2. **Check code quality**: Run `make check` and `make typecheck`
+3. **Update tests**: Add tests for new features or bug fixes
+4. **Update documentation**: Document new features in `docs/source/`
+
+### Commit Messages
+
+- Keep commits concise (max 3 lines preferred)
+- Focus on what changed and why
+- Write as if a human developer wrote them
+- **Never mention AI assistance or Claude in commits**
+- Use standard git conventions
+
+**Good examples**:
+```
+Fix UV_PYTHON default value to prevent empty parameter error
+
+Add migration guide documenting breaking changes
+```
+
+**Bad examples**:
+```
+Fixed stuff with Claude's help
+
+Updated code (generated with AI)
+```
+
+### Submitting
+
+1. Create a feature branch: `git checkout -b feature/my-feature`
+2. Make your changes and commit
+3. Push to GitHub: `git push origin feature/my-feature`
+4. Open a Pull Request on GitHub
+5. Wait for CI to pass and address review feedback
+
 ## Copyright & Licence
 
-- Copyright (c) 2022-2024 MXStack Contributors
+- Copyright (c) 2022-2025 MXStack Contributors
 - under 2-Clause BSD License (aka Simplified BSD License)
 - see LICENSE.md