Core exposes buildIndex/searchText/executeQuery/executeAttune as the single shared
implementation for all transports. First TypeScript module, run via Node type
stripping in dev. Adds typescript-eslint. lint/typecheck green, test 107/107.
Root package.json (type: module), strict tsconfig with allowJs/checkJs:false for
gradual migration, flat ESLint config scoped to scripts/ + tests/. App untouched.
All three green: lint, typecheck, test 107/107.