System prompt instructs the agent to take trip inputs, candidate pool,
and optional prior draft + change request, perform web research, then
return ONLY a JSON object matching ItineraryDraft schema (destination,
start_date, end_date, items[] with name/category/lat/lng/address/day_index/why/est_cost).
Mirrors recruiter-triage file format/structure.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
