fix: run build before typecheck in CI

The demo app resolves react-virtualized-diff types from dist/index.d.ts,
which doesn't exist on a fresh checkout until build runs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Zhang-JiahangH

.github/workflows/ci.yml

@@ -22,6 +22,6 @@ jobs:
 
       - run: pnpm install --frozen-lockfile
       - run: pnpm lint
+      - run: pnpm build
       - run: pnpm typecheck
-      - run: pnpm test
-      - run: pnpm build
+      - run: pnpm test