Add unit tests for strategy selector (17), lite compression (20), stats module (11), and DB module (7). Add integration tests for full compression pipeline (6). All 61 tests pass. Remove broken integration test files from previous WIP.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
