feat: add automated test suite and pytest infrastructure to prevent regressions

[bhavyakeerthi3]

Description

This PR addresses issue #134 by introducing an automated test suite using pytest.
This provides critical coverage for configuration parsing and retrieval logic,
ensuring stability and preventing future regressions.

Related Issue

Closes #134

Changes

• Testing Infrastructure: Added tests/ directory with conftest.py and test_health.py.
• Config Testing: Added test_config.py to verify Pydantic models, fallbacks, and feature flags.
• Retrieval Testing: Added test_retrieval.py for unit testing retrieval helpers.
• Dependencies: Added pytest and pytest-mock to pyproject.toml.

Verification

Verified locally with python -m pytest tests -v. All core logic tests passed.

[adamjohnwright]

Thank you — this was correct, and it is now fixed on main (#167), arrived at independently during a tooling pass before I had read your PR properly. Apologies for the duplicated effort.

Closing as already resolved rather than stale.