ci: build @ai-dm/engine before typecheck/test in the deploy workflow

The test job resolved @ai-dm/engine via its dist, which wasn't built in CI.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: SociableSteve

.github/workflows/deploy.yml

@@ -27,6 +27,7 @@ jobs:
           node-version: 22
           cache: npm
       - run: npm ci
+      - run: npm run build --workspace @ai-dm/engine # other packages resolve @ai-dm/engine via its dist
       - run: npm run typecheck
       - run: npm test