feat: source-derived Q&A with statewide CA ocean species coverage (#1)

feat: add official source cache foundation

test: allow sourced dungeness open season answers

test: broaden dungeness fallback guard

test: use semantic dungeness fallback guard

test: scope dungeness fallback to direct answer

test: narrow certification forbidden terms

test: narrow safety forbidden phrases

test: reduce real query fixture brittleness

test: separate real query assertion buckets

test: add real CoastWise query fixture