Devin Review (post-merge on PR #6) flagged that the `final_result`
assignment used a truthiness check (`if job_row.result`) while
`build_initial_result` used an identity check (`is None`). For a
job whose result is an empty dict (`{}`), the emitted
`GroundTruthSample` ended up with `initial_result={}` but
`final_result=None` — logically inconsistent.
Switch the final-result assignment to the same `is None` check so
both fields agree. Added `test_empty_dict_result_stays_consistent`
to lock the invariant in, and fixed the test helper so callers can
pass `{}` without the helper's `or` fallback replacing it.
Co-Authored-By: adrian kuman firmansah <adriancuman@gmail.com>