Integrate UCI: AI review, AI assistant, and stale check - #13

Well-scoped, well-documented first CI for this repo: three UCI callers pinned to a commit SHA plus a genuinely useful REVIEW.md whose claims about install.sh and tests/run.ts I verified against the tree and found accurate. No blockers, but the stale-check job's permissions: block silently drops contents: read, the README's new "reviewed automatically" claim won't hold for fork PRs, and none of the workflows set a caller-level concurrency group.