fix: reject non-VPCS nodes in the VPCS config tool

VPCS syntax typed into another node's console is silently discarded
(IOS answers % Invalid input) while the tool still reports success.
get_device_ports_from_topology now carries the GNS3 node type through
to callers, and VPCSCommands fails device preparation with a per-device
error unless the node type is vpcs.

tests/agent/mcp/test_device_tools.py

@@ -0,0 +1,65 @@
+"""
+Device config tool tests with mocked topology and Nornir layers.
+
+Covers the VPCS node-type guard and the error contract shared by
+device_config_send / device_show_run / vpcs_config_set.
+"""
+import json
+
+import pytest
+from unittest.mock import MagicMock, patch
+
+VPCS_MOD = "gns3server.agent.gns3_copilot.tools_v2.vpcs_tools_netmiko"
+
+
+def _topology_ports(node_type):
+    """Mocked get_device_ports_from_topology return value for one device."""
+    return {"PC1": {"port": 5000, "node_type": node_type}}
+
+
+class TestVPCSNodeTypeGuard:
+
+    def test_non_vpcs_node_is_rejected(self):
+        from gns3server.agent.gns3_copilot.tools_v2.vpcs_tools_netmiko import VPCSCommands
+
+        with patch(f"{VPCS_MOD}.get_device_ports_from_topology",
+                   return_value=_topology_ports("iou")) as topo:
+            result = VPCSCommands()._run(json.dumps({
+                "project_id": "0c0fde25-6ead-4413-a283-ea8fd2324291",
+                "device_configs": [{"device_name": "PC1", "commands": ["ip 10.0.0.1/24"]}],
+            }))
+            assert topo.called
+        assert len(result) == 1
+        assert result[0]["device_name"] == "PC1"
+        assert result[0]["status"] == "failed"
+        assert "not a VPCS node" in result[0]["error"]
+
+    def test_missing_node_type_is_rejected(self):
+        from gns3server.agent.gns3_copilot.tools_v2.vpcs_tools_netmiko import VPCSCommands
+
+        with patch(f"{VPCS_MOD}.get_device_ports_from_topology",
+                   return_value={"PC1": {"port": 5000}}):
+            result = VPCSCommands()._run(json.dumps({
+                "project_id": "0c0fde25-6ead-4413-a283-ea8fd2324291",
+                "device_configs": [{"device_name": "PC1", "commands": ["ip 10.0.0.1/24"]}],
+            }))
+        assert result[0]["status"] == "failed"
+        assert "unknown-type" in result[0]["error"]
+
+    def test_vpcs_node_passes_the_guard(self):
+        from gns3server.agent.gns3_copilot.tools_v2.vpcs_tools_netmiko import VPCSCommands
+
+        tool = VPCSCommands()
+        nornir = MagicMock()
+        host_result = MagicMock(failed=False)
+        host_result.result = "OK"
+        nornir.run.return_value = {"PC1": host_result}
+        with patch(f"{VPCS_MOD}.get_device_ports_from_topology",
+                   return_value=_topology_ports("vpcs")), \
+             patch.object(VPCSCommands, "_initialize_nornir", return_value=nornir):
+            result = tool._run(json.dumps({
+                "project_id": "0c0fde25-6ead-4413-a283-ea8fd2324291",
+                "device_configs": [{"device_name": "PC1", "commands": ["ip 10.0.0.1/24"]}],
+            }))
+        assert result[0]["status"] == "success"
+        assert result[0]["output"] == "OK"