Function register_task_with_mcp 

pub fn register_task_with_mcp(
    registry: &Arc<ToolRegistry>,
    llm_client: Arc<dyn LlmClient>,
    agent_registry: Arc<AgentRegistry>,
    workspace: String,
    mcp_manager: Option<Arc<McpManager>>,
)

Register the task delegation tools with optional MCP manager.

When mcp_manager is provided, child subagent sessions will have access to all MCP tools from connected servers.