fix(typing): resolve mypy errors in agent node lifecycle tools

gns3server/agent/gns3_copilot/tools_v2/gns3_start_node.py

@@ -136,7 +136,11 @@ class GNS3StartNodeTool(BaseTool):
             results = []
             known_ids = [nid for nid in node_ids if nid in nodes_by_id]
             start_results = start_node_handler({"project_id": project_id, "node_ids": known_ids}, gns3_ctx)
-            start_errors = {r["node_id"]: r.get("error") for r in start_results if r.get("status") == "error"}
+            start_errors = (
+                {r["node_id"]: r.get("error") for r in start_results if r.get("status") == "error"}
+                if isinstance(start_results, list)
+                else {}
+            )
 
             # Get immediate status (likely 'starting' or 'stopped') — one call
             listing = get_nodes_handler({"project_id": project_id}, gns3_ctx)