v3: streaming SSE + async batch API (12 new tests, 138 total)

Tasks 5-7: eval harness, FastAPI backend, Paper & Ink UI- src/eval/ — precision/recall/F1 harness with type-aware comparators,micro/macro F1, CSV + markdown reports, --model benchmark flag- src/api/ — FastAPI backend with /extract, /schemas, /health,request-ID middleware, typed error envelope, injectable extractor- ui/ — Vite + React + TS + Tailwind + Motion + React Three FiberPaper & Ink editorial UI with 3D paper hero, dark/light mode,confidence inkwell, wax-stamp metrics, kinetic typography- 95 passing tests (up from 54); UI is a separate npm workspace

Initial commit: schemas, extraction engine, dataset prep, 54 passing tests