Filters select prime records, but subaward_count and subaward_obligation
cover all reported subawards under each prime, not just subaward actions
within time_period_start/end. This ranking is not a fiscal-period
subaward ranking. For dated reports, pass a returned
award_generated_internal_id to search_subawards(award_id=...), read every
page, and retain action_date values inside the desired period.

sort accepts: award_id, subaward_count, award_generated_internal_id,
subaward_obligation. (These differ from search_subawards, which sorts by
amount/action_date/etc.) Anything else returns HTTP 400 from the API.

page_metadata.hasNext is worked out here: the endpoint itself always
says false, even with more pages. Rows include primes with no
subawards (subaward_count 0). subaward_obligation sums FFATA reports,
which can repeat cumulative amounts, so a subaward_to_award_ratio
above 1 is a reporting artefact, not more subcontracting than the prime.

program_numbers filters assistance awards by assistance listing (CFDA)
number, e.g. ['93.778'] for Medicaid; use it with award_type='grants',
'loans', 'direct_payments', or 'other'. autocomplete_cfda() finds numbers
by program name.