Function register_task 

pub fn register_task(
    registry: &Arc<ToolRegistry>,
    llm_client: Arc<dyn LlmClient>,
    agent_registry: Arc<AgentRegistry>,
    workspace: String,
)

Register the task delegation tools (task, parallel_task).

Must be called after the registry is wrapped in Arc. Requires an LLM client and the workspace path so child agent loops can be spawned inline. Optionally accepts an MCP manager so child sessions inherit MCP tools.