fix: add proxy-args to stdio_mcp_tool schema top-level properties (#25542)

Author: Copilot

pkg/parser/schemas/main_workflow_schema.json

@@ -9623,6 +9623,13 @@
             "type": "string"
           },
           "examples": [["*"], ["store_memory", "retrieve_memory"], ["brave_web_search"]]
+        },
+        "proxy-args": {
+          "type": "array",
+          "items": {
+            "type": "string"
+          },
+          "description": "Custom proxy arguments for container-based MCP servers (e.g., DIFC proxy configuration)"
         }
       },
       "additionalProperties": false,