Add a minimal quality gate

[5aumit]

Outcome

Every pull request gets a small, repeatable check that catches lint, test, and packaging regressions. New tests are never silently ignored by Git.

Scope

• Make the documented Ruff command pass.
• Remove the rule that ignores new files under tests/.
• Add GitHub Actions checks for Ruff, Pytest, and a package build.
• Keep the workflow simple and aligned with the documented Python version.

Out of scope

• Coverage targets, deployment automation, or a large release process.
• Reformatting unrelated source code.

Blocked by

Nothing.

[5aumit]

Current-code references

• New test files are currently ignored by Git through this repository rule: .gitignore:18-19.
• Ruff and Pytest are already configured in the project: pyproject.toml:37-46.

There is no committed GitHub Actions workflow yet, so that missing automation has no source-file citation. This ticket adds it.