src/lib/countries.ts imported the full iso-3166 package solely to build
a Set of valid ISO 3166-2 subdivision codes for validation. That dataset
(~5000 objects with names, parents, and tree structure) landed in the
eagerly-preloaded countries chunk because NoteContent, ComposeBox, and
campaign.ts all import from countries.ts on the critical path.
Ship only the subdivision code strings instead, generated at build time
into src/lib/subdivisionCodes.ts via scripts/gen-subdivision-codes.mjs.
iso-3166 moves to devDependencies since only the generator script needs
it now. The strict-validation contract (rejecting US-ZZ etc.) is
preserved.
Alex Gleason