[HoungDev]

Summary

• add a discoverable contributor entry point in the README with live good first issue and help wanted searches
• expand the contributor guide from issue selection through cross-platform setup, validation, and review
• update the pull request template to request a linked issue, motivation, compatibility or safety impact, exact validation, and a focused checklist

Why

The repository had the necessary community files, but a first-time contributor still had to infer how to claim work, verify the setup, handle demo changes, and provide review-ready evidence. This creates avoidable friction around the two v0.2.0 issues intentionally reserved for outside contributors.

Impact

This is documentation and repository-template only. It does not change runtime behavior, packaging metadata, releases, or ownership of issue #15 or #18. Security reports continue to route to private vulnerability reporting.

Verification

• git diff --check
• ruff check .
• ruff format --check .
• pytest — 85 passed, 94.02% coverage
• wheel and sdist built successfully
• twine check passed for both distributions

Closes #21