feat(orchestrator): Implement Delegate node for task routing

backend/src/ea_chatbot/graph/nodes/delegate.py

@@ -0,0 +1,18 @@
+from ea_chatbot.graph.state import AgentState
+from ea_chatbot.utils.logging import get_logger
+
+def delegate_node(state: AgentState) -> dict:
+    """Determine which worker subgraph to call next based on the checklist."""
+    checklist = state.get("checklist", [])
+    current_step = state.get("current_step", 0)
+    logger = get_logger("orchestrator:delegate")
+    
+    if not checklist or current_step >= len(checklist):
+        logger.info("Checklist complete or empty. Routing to summarizer.")
+        return {"next_action": "summarize"}
+    
+    task_info = checklist[current_step]
+    worker = task_info.get("worker", "data_analyst")
+    
+    logger.info(f"Delegating next task to worker: {worker}")
+    return {"next_action": worker}

backend/tests/test_orchestrator_delegate.py

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+from ea_chatbot.graph.nodes.delegate import delegate_node
+from ea_chatbot.graph.state import AgentState
+
+def test_delegate_node_data_analyst():
+    """Verify that the delegate node routes to data_analyst."""
+    state = AgentState(
+        checklist=[{"task": "Analyze data", "worker": "data_analyst"}],
+        current_step=0,
+        messages=[],
+        question="test",
+        analysis={},
+        next_action="",
+        iterations=0,
+        vfs={},
+        plots=[],
+        dfs={}
+    )
+    
+    result = delegate_node(state)
+    assert result["next_action"] == "data_analyst"
+
+def test_delegate_node_researcher():
+    """Verify that the delegate node routes to researcher."""
+    state = AgentState(
+        checklist=[{"task": "Search web", "worker": "researcher"}],
+        current_step=0,
+        messages=[],
+        question="test",
+        analysis={},
+        next_action="",
+        iterations=0,
+        vfs={},
+        plots=[],
+        dfs={}
+    )
+    
+    result = delegate_node(state)
+    assert result["next_action"] == "researcher"
+
+def test_delegate_node_finished():
+    """Verify that the delegate node routes to summarize if checklist is complete."""
+    state = AgentState(
+        checklist=[{"task": "Task 1", "worker": "data_analyst"}],
+        current_step=1, # Already finished the only task
+        messages=[],
+        question="test",
+        analysis={},
+        next_action="",
+        iterations=0,
+        vfs={},
+        plots=[],
+        dfs={}
+    )
+    
+    result = delegate_node(state)
+    assert result["next_action"] == "summarize"