Scaffold youaskm3 web React UI shell

[enricopiovesan]

Summary

Create the initial React app shell for youaskm3 at apps/youaskm3/web-react with no Traverse business logic, configured for local runtime connection via .traverse/server.json.

Why

youaskm3 needs a browser-hosted UI shell that the runtime HTTP client and knowledge workflow UI will build on top of. The shell must be clean, typed, and locally runnable before any integration work starts.

Definition of Done

• apps/youaskm3/web-react exists with React 18 + TypeScript + Vite + Vitest + ESLint
• .nvmrc pins Node version
• npm run dev starts the app locally
• npm run typecheck and npm run lint pass clean
• No Traverse business logic present
• README documents local setup and TRAVERSE_REPO override

Depends on

#10 (youaskm3 plan), #2 (traverse-starter scaffold — reuse toolchain decisions)