Improve grounded project discovery - #71

What changed

• unify Discover, Tool Intelligence, and repository detail pages on the shared app shell
• ground project recommendations in meaningful similar repositories and exclude weak or conflicting tool evidence
• add semantic and lexical discovery fusion, bounded tool pagination, and reliable request cancellation
• make public previews catalog-first with a clear sign-in boundary for uncataloged repositories
• add production-shaped desktop and mobile browser coverage and synchronize product, privacy, CI, and OpenSpec documentation

Why

Starboard should help people discover credible projects and tools for their own repositories. The previous surfaces were visually inconsistent, some first requests could cancel themselves, and recommendation evidence could be too weak or misleading.

Validation

• pnpm lint
• pnpm typecheck
• pnpm docs:check
• pnpm test:coverage (185 tests; selective core modules at 100%)
• pnpm build:e2e
• CI=1 pnpm test:e2e (14 desktop/mobile journeys)
• pnpm build:cf
• pnpm knip:strict
• pnpm audit --prod
• openspec validate --all --strict
• git diff --check