Install tea pr index step.

.gitea/workflows/auto-pr-tofu-plan.yml

@@ -84,6 +84,15 @@ jobs:
             exit 1
           fi
 
+          pr_index=$(tea pr list \
+          --repo ${{ github.repository }} \
+          --state open \
+          --fields index,head \
+          --output simple \
+          | awk '{print $1}')
+
+          echo ${pr_index}
+          echo "pr_number=$pr_index" >> "$GITHUB_OUTPUT"
 
       - name: Generate .env from Hashicorp Vault
         uses: https://git.trez.wtf/Trez/hc-vault-env@main