chore: import upstream snapshot with attribution

.github/CONTRIBUTING.md

@@ -0,0 +1,85 @@
+# Contributing to `docmd`
+
+
+Thank you for your interest in contributing to `docmd`! We appreciate all contributions, from bug fixes and documentation improvements to new features and design suggestions.
+
+## Development Environment
+
+`docmd` is a monorepo managed with [pnpm](https://pnpm.io/).
+
+### Prerequisites
+
+- **Node.js**: v22.x or later (LTS recommended)
+- **pnpm**: v10.x or later
+
+### Project Setup
+
+Clone the repository and set up the development environment:
+
+```bash
+git clone https://github.com/docmd-io/docmd.git
+cd docmd
+pnpm prep
+```
+
+To also link the local `docmd` command globally for testing in other projects:
+
+```bash
+pnpm prep --link
+```
+
+### Local Development
+
+Run the documentation site while watching for changes in the core engine:
+
+```bash
+pnpm run dev
+```
+
+To watch internal source files (engine, templates, and plugins), set the `DOCMD_DEV` environment variable:
+
+```bash
+DOCMD_DEV=true pnpm run dev
+```
+
+## Quality Standards
+
+Before submitting a Pull Request, please ensure your changes pass the verification suite:
+
+```bash
+pnpm verify
+```
+
+### Commit Guidelines
+
+We use [Conventional Commits](https://www.conventionalcommits.org/). Please prefix your commit messages with:
+- `feat:` (New features)
+- `fix:` (Bug fixes)
+- `docs:` (Documentation changes)
+- `refactor:` (Code changes that neither fix bugs nor add features)
+
+### Source Headers
+
+All new files within the `packages/` directory MUST include the standard project copyright header to maintain consistency and compliance.
+
+```javascript
+/**
+ * --------------------------------------------------------------------
+ * docmd : the minimalist, zero-config documentation generator.
+ *
+ * @package     @docmd/core (and ecosystem)
+ * @website     https://docmd.io
+ * @repository  https://github.com/docmd-io/docmd
+ * @license     MIT
+ * @copyright   Copyright (c) 2025-present docmd.io
+ *
+ * [docmd-source] - Please do not remove this header.
+ * --------------------------------------------------------------------
+ */
+```
+
+## GitHub Workflow
+
+1.  **Fork and Branch**: Create a feature branch from the latest `main`.
+2.  **Verify**: Ensure `pnpm verify` returns `🛡️ docmd is ready for production!`.
+3.  **Pull Request**: Open a PR with a clear description of the problem solved or the feature added.