build(deps): pin docker/cagent-action back to v1.5.1

v1.5.2's review-pr/action.yml has a YAML parse error at line 822 that
breaks the PR review workflow. Tracking upstream at
docker/cagent-action#205.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/nightly-docs-scan.yml

@@ -66,7 +66,7 @@ jobs:
           echo "GITHUB_APP_TOKEN=$PAT" >> "$GITHUB_ENV"
 
       - name: Run documentation scan
-        uses: docker/cagent-action@2a43a3882401f45e3114df7f6d66eca184993a90 # latest
+        uses: docker/cagent-action@0498757af1c50b084f763d626f571918cf317509 # v1.5.1
         env:
           GH_TOKEN: ${{ env.GITHUB_APP_TOKEN || github.token }}
         with:

.github/workflows/pr-review.yml

@@ -14,7 +14,7 @@ jobs:
     if: |
       github.event_name == 'issue_comment' ||
       github.event.workflow_run.conclusion == 'success'
-    uses: docker/cagent-action/.github/workflows/review-pr.yml@2a43a3882401f45e3114df7f6d66eca184993a90 # v1.5.2
+    uses: docker/cagent-action/.github/workflows/review-pr.yml@0498757af1c50b084f763d626f571918cf317509 # v1.5.1
     # Scoped to the job so other jobs in this workflow aren't over-permissioned
     permissions:
       contents: read # Read repository files and PR diffs