💡 Motivation and Context

The local development instructions in this repo lived in the main README.

This PR moves them into a dedicated CONTRIBUTING.md so contributors have a consistent place to find setup and test commands.

💚 How did you test it?

• Not run (docs-only changes)
• Checked the updated markdown links and file locations

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Added the release label to the PR
• Added exactly one version bump label: bump-patch, bump-minor, or bump-major