chore(deps): pin boneskull/gh-stack action to a9af01a

Author: renovate[bot]

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

@@ -22,7 +22,7 @@ jobs:
       # Action definition is always fetched from main, so PRs that edit it
       # don't affect the running version until merged.
       - name: Run Claude Code Review
-        uses: boneskull/gh-stack/.github/actions/claude-code-review@main
+        uses: boneskull/gh-stack/.github/actions/claude-code-review@a9af01a1e7f39896023bd5d7cecfbcb2a9744668 # main
         with:
           claude_code_oauth_token: ${{ secrets.CLAUDE_CODE_OAUTH_TOKEN }}
           repository: ${{ github.repository }}