Citation verification
Phase 4 output: each specialist claim searched independently against PubMed (NCBI E-utilities, called directly from the Worker) and judged — conservatively — for whether a real paper substantiates the specific claim, not just its topic. "No match" is the expected outcome for most claims, not a failure.
This is a signal, not an automatic evidence-tier promotion — a strong match here still needs human/clinical review before anything is presented to a user as verified.