feat: implement subagent delegation for task management

- Introduced the `delegate_task` tool, allowing the main agent to spawn child AIAgent instances with isolated context for complex tasks.
- Supported both single-task and batch processing (up to 3 concurrent tasks) to enhance task management capabilities.
- Updated configuration options for delegation, including maximum iterations and default toolsets for subagents.
- Enhanced documentation to provide clear guidance on using the delegation feature and its configuration.
- Added comprehensive tests to ensure the functionality and reliability of the delegation logic.

cli.py

@@ -139,6 +139,10 @@ def load_cli_config() -> Dict[str, Any]:
             "timeout": 300,    # Max seconds a sandbox script can run before being killed (5 min)
             "max_tool_calls": 50,  # Max RPC tool calls per execution
         },
+        "delegation": {
+            "max_iterations": 25,  # Max tool-calling turns per child agent
+            "default_toolsets": ["terminal", "file", "web"],  # Default toolsets for subagents
+        },
     }
     
     # Track whether the config file explicitly set terminal config.