fix: ensure benchmark results are uploaded and commented on failure (#673)

- Add 'if: always()' to save and upload benchmark results steps so
  artifacts are available even when the benchmark fails
- Update benchmark-comment workflow to only trigger when the benchmark
  run concludes with failure

Author: bnusunny

.github/workflows/benchmark-comment.yaml

@@ -12,7 +12,7 @@ permissions:
 jobs:
   comment:
     runs-on: ubuntu-24.04
-    if: github.event.workflow_run.event == 'pull_request'
+    if: github.event.workflow_run.event == 'pull_request' && github.event.workflow_run.conclusion == 'failure'
     steps:
       - name: Download benchmark results
         uses: actions/download-artifact@v4

.github/workflows/benchmark.yaml

@@ -90,13 +90,15 @@ jobs:
           fi
 
       - name: Save benchmark results
+        if: always()
         run: |
           mkdir -p benchmark-results
           cp $GITHUB_STEP_SUMMARY benchmark-results/summary.md
           echo "${{ github.event.pull_request.number }}" > benchmark-results/pr_number.txt
           echo "${{ steps.compare.outputs.regression }}" > benchmark-results/regression.txt
 
       - name: Upload benchmark results
+        if: always()
         uses: actions/upload-artifact@v4
         with:
           name: benchmark-results