perf(review): cancel in-progress reviews on new push

Author: zfarrell

.github/workflows/claude-pr-review.yml

@@ -4,6 +4,10 @@ on:
   pull_request:
     types: [opened, synchronize, ready_for_review, reopened]
 
+concurrency:
+  group: pr-review-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
 jobs:
   review:
     if: github.event.pull_request.draft == false