Use unique concurrency group for bot review runs

Job-level `if` doesn't prevent the workflow run from being created,
so the concurrency group still cancels in-progress runs. Fix by
giving bot review runs a unique concurrency group (appending run_id)
so they can't cancel real benchmark runs.

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

Author: sbryngelson

.github/workflows/bench.yml

@@ -7,7 +7,7 @@ on:
   workflow_dispatch:
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
+  group: ${{ github.workflow }}-${{ github.ref }}${{ github.event_name == 'pull_request_review' && github.event.review.user.type == 'Bot' && format('-bot-{0}', github.run_id) || '' }}
   cancel-in-progress: true
 
 jobs: