FIPS-with-column hold counts from loaded engine tables. Not a fill percent.

Walks the already-loaded engine table catalog with the same _type_is_held the query path uses. Each slot is a FIPS count of a column that exists on at least one loaded county table, not a frozen list and not health counties_loaded. Absentee is held only when both owner_address and site_address exist. Optional ?fips= returns the per-county boolean map. Does not advertise fields absent from loaded county tables (tax_amount, subdivision_name, FEMA/EPA stay out unless a table holds them). No national fill percent.