[P2] No automated test suite for any microservice

Problem

The codebase has no automated tests. The only test file (http-service/test.py) is a manual endpoint test, not a proper unit or integration test. There are no tests for the dataprep pipeline, retriever, reranker, or ChatQnA orchestrator.

Files

• http-service/test.py — Manual test, not an automated test suite
• retriever/PROPOSED_TEST_STRATEGY.md — Test strategy document exists but no tests are implemented

Acceptance Criteria

• Create unit tests for GenieTEIReranking (reranking strategies: slice, threshold, knee_threshold)
• Create unit tests for GenieArangoDataprep (labeling strategies, content validation)
• Create integration tests for the dataprep microservice endpoints
• Create unit tests for UserContextBuilder (sanitization, DoB parsing, age calculation)
• Implement the proposed retriever test strategy from PROPOSED_TEST_STRATEGY.md
• Add a test runner script and minimum coverage threshold to CI