Add checkout step to issue triage workflow

Added a checkout step to the GitHub Actions workflow for issue triage
to ensure the repository is available during the triage process.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.github/workflows/claude-issue-triage.yml

@@ -13,6 +13,9 @@ jobs:
       issues: write
 
     steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
       - name: Create triage prompt
         run: |
           mkdir -p /tmp/claude-prompts