fix: repair SSH key step quoting in workflows

.gitea/workflows/kubeadm-reset.yml

@@ -53,7 +53,12 @@ jobs:
             exit 1
           fi
 
-          KEY_CONTENT="$KEY_CONTENT" python3 -c 'import os, pathlib; key=os.environ.get("KEY_CONTENT", "").replace("\r", "").strip(); key=key[1:-1] if len(key) > 2 and ((key[0] == "\"" and key[-1] == "\"") or (key[0] == "\'" and key[-1] == "\'")) else key; key=key.replace("\\n", "\n") if "\\n" in key and "\n" not in key else key; pathlib.Path.home().joinpath(".ssh", "id_ed25519").write_text(key if key.endswith("\n") else key + "\n")'
+          KEY_CONTENT="$(printf '%s' "$KEY_CONTENT" | tr -d '\r')"
+          if printf '%s' "$KEY_CONTENT" | grep -q '\\n'; then
+            printf '%b' "$KEY_CONTENT" > ~/.ssh/id_ed25519
+          else
+            printf '%s\n' "$KEY_CONTENT" > ~/.ssh/id_ed25519
+          fi
           chmod 0600 ~/.ssh/id_ed25519
 
           if ! ssh-keygen -y -f ~/.ssh/id_ed25519 >/dev/null 2>&1; then