"//":"Server-side type-checking. Node 25 runs .ts natively (type-stripping), so there is NO build step — this config only type-checks (noEmit). Migration is incremental (like the client): allowJs + checkJs:false means only .ts server files are checked; the remaining .js run untouched. Migrated modules are ESM (.ts) and are required from .js callers via Node's require(esm).",