Add contributing guidelines in CONTRIBUTING.md

CONTRIBUTING.md

@@ -0,0 +1,90 @@
+# Contributing to agent-runtime
+
+Thanks for taking the time to contribute! This project is maintained by a single person, so community help is genuinely appreciated.
+
+## Getting Started
+
+1. Fork the repository and clone your fork.
+2. Make sure you have the Rust toolchain installed (see [rust-toolchain.toml](rust-toolchain.toml) for the required version).
+3. Build and run the tests to confirm everything works:
+
+```powershell
+cargo build
+cargo test
+```
+
+## How to Contribute
+
+### Bug Reports
+
+Open a [GitHub issue](../../issues/new) with:
+- A clear description of the problem
+- Steps to reproduce
+- Expected vs. actual behavior
+- Rust version and OS
+
+### Feature Requests
+
+Open an issue first to discuss the idea before writing code. This avoids wasted effort if the feature doesn't align with the project direction.
+
+### Pull Requests
+
+1. Open an issue or comment on an existing one so we can discuss the approach.
+2. Create a branch from `main` with a descriptive name (e.g. `fix/tool-loop-timeout`, `feat/openai-provider`).
+3. Keep changes focused, one concern per PR.
+4. Run the full test suite and lints before submitting:
+
+```powershell
+cargo test --all-features
+cargo clippy --all-targets --all-features -- -D warnings
+cargo fmt --all --check
+```
+
+5. Write or update tests for any changed behavior.
+6. Open the PR against `main` with a clear description of what changed and why.
+
+## Commit Message Format
+
+This project follows the Conventional Commits Specification v1.0.0.
+
+Reference:
+https://www.conventionalcommits.org/en/v1.0.0/#specification
+
+Use this format for commit messages:
+
+```text
+<type>[optional scope]: <description>
+
+[optional body]
+
+[optional footer(s)]
+```
+
+Common types used in this repository:
+- `feat` for new features
+- `fix` for bug fixes
+- `docs` for documentation changes
+- `chore` for maintenance tasks
+- `refactor` for code changes that do not add features or fix bugs
+- `test` for adding or updating tests
+- `perf` for performance improvements
+- `ci` for CI pipeline or automation changes
+
+Examples:
+- `docs: add security and contributing guides`
+- `fix(config): handle missing yaml file path`
+- `feat(runtime): add workflow retry strategy options`
+
+## Security Vulnerabilities
+
+Please do **not** open public issues for security bugs. See [SECURITY.md](SECURITY.md) for how to report them privately.
+
+## Code Style
+
+- Follow standard Rust idioms and the project's existing patterns.
+- Run `cargo fmt` before committing.
+- Clippy warnings are treated as errors, fix them rather than suppressing them unless there is a good reason.
+
+## License
+
+By contributing, you agree that your contributions will be licensed under the same terms as this project: [MIT](LICENSE-MIT) or [Apache-2.0](LICENSE-APACHE), at the user's option.