fix: fail fast when terraform node IP outputs are empty

nixos/kubeadm/scripts/render-inventory-from-tf-output.py

@@ -18,6 +18,28 @@ def map_to_pairs(items: dict[str, str]) -> str:
     return " ".join(f"{k}={v}" for k, v in ordered)
 
 
+def require_non_empty_ips(label: str, items: dict[str, str]) -> dict[str, str]:
+    cleaned: dict[str, str] = {}
+    missing: list[str] = []
+
+    for name, ip in items.items():
+        ip_value = (ip or "").strip()
+        if not ip_value:
+            missing.append(name)
+            continue
+        cleaned[name] = ip_value
+
+    if missing:
+        names = ", ".join(sorted(missing, key=natural_key))
+        raise SystemExit(
+            f"Missing IPv4 addresses for {label}: {names}. "
+            "Terraform outputs are present but empty. "
+            "This usually means Proxmox guest IP discovery is unavailable for these VMs yet."
+        )
+
+    return cleaned
+
+
 def main() -> int:
     payload = json.load(sys.stdin)
 
@@ -27,6 +49,9 @@ def main() -> int:
     if not cp_map or not wk_map:
         raise SystemExit("Missing control_plane_vm_ipv4 or worker_vm_ipv4 in terraform output")
 
+    cp_map = require_non_empty_ips("control planes", cp_map)
+    wk_map = require_non_empty_ips("workers", wk_map)
+
     ssh_user = os.environ.get("KUBEADM_SSH_USER", "").strip() or "micqdf"
 
     print(f"SSH_USER={ssh_user}")