ci: remove holon-review workflow; gate auto_review via trigger var

Author: jolestar

.github/workflows/holon-review.yml

@@ -28,6 +28,8 @@ jobs:
       assignee_login: ${{ github.event.assignee.login || '' }}
       comment_id: ${{ github.event.comment.id || 0 }}
       review_id: ${{ github.event.review.id || 0 }}
+      # Optional: enable auto-review for every PR when true
+      auto_review: false
       # Optional: Specify custom runner labels.
       # Plain string for single label (e.g., 'self-hosted' or 'ubuntu-24.04-large'):
       # runs_on: 'self-hosted'