chore: add CONTRIBUTING.md and LICENSE

[Arvuno]

Summary

This PR adds two missing project health files:

• CONTRIBUTING.md — contribution guidelines with development setup, PR process, and code quality standards
• LICENSE — MIT license

Both files are standard for open-source projects and help contributors understand how to engage with the project.

Changes

• CONTRIBUTING.md — new file (guidelines for submitting PRs, issues, and code standards)
• LICENSE — new file (MIT License)

Testing

No code changes — documentation-only. CI/CD is not affected.

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Summary by cubic

Adds CONTRIBUTING.md with development setup, PR workflow, and code standards, plus an MIT LICENSE to formalize project licensing. Improves contributor onboarding and compliance; no code changes.

^{Written for commit b25daca. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

No issues found across 3 files

_{Re-trigger cubic}