Allow null sandbox.agent in workflow schema (#53293)

Author: github-actions[bot]

pkg/parser/schemas/main_workflow_schema.json

@@ -3525,6 +3525,10 @@
               "description": "Agent sandbox type: 'awf' uses AWF (Agent Workflow Firewall), or false to disable agent sandbox. Defaults to 'awf' if not specified. Note: Disabling the agent sandbox (false) removes firewall protection but keeps the MCP gateway enabled.",
               "default": "awf",
               "oneOf": [
+                {
+                  "type": "null",
+                  "description": "Null (an empty 'agent:' key) leaves the agent sandbox at its default of 'awf'"
+                },
                 {
                   "type": "boolean",
                   "const": false,