add SSH key to agent

.forgejo/workflows/cd.yaml

@@ -13,12 +13,14 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Set up SSH key to access age secrets
+      - name: Set up SSH key for age secrets and SSH
         run: |
           env
           mkdir -p ~/.ssh
           echo "${{ secrets.CD_SSH_KEY }}" > ~/.ssh/id_ed25519
           chmod 600 ~/.ssh/id_ed25519
+          eval "$(ssh-agent -s)"
+          ssh-add ~/.ssh/id_ed25519
 
       - name: Deploy
         run: nix-shell --run 'nixops4 apply default'