Add scripts/healthcare_email_streams.py as the single source of truth for
classifying NPPES-endpoint emails into institutional (HOT stream) / consumer
(trucking-discipline stream) / direct (DirectTrust, parked), plus an exclude set
for non-prospect giants (va.gov, *.mil, cvshealth, walgreens, walmart).
Rework build_npi_outreach_lists.py to emit one CSV per stream
(npi_healthcare_institutional/consumer + npi_direct_secure), overdue-first
sorted, with companion files (revalidation/leie/optout) now optional.
Verified on May 2026 NPPES endpoint_pfile: 89,557 institutional / 19,366 consumer
/ 242,441 direct rows.
