Refactor workflow agent and routing components for improved functionality

- Introduce WorkflowAgentStage to manage agent stage configurations and enhance interaction with the workflow engine.
- Implement WorkflowEdgeEvaluator for priority-aware edge evaluation, improving routing decisions based on conditions and user turns.
- Update WorkflowBrain to handle user turns and routing more effectively, ensuring agents cannot have only one default path.
- Enhance CallEndCoordinator to track speech events and manage call termination based on queued speech.
- Add new models and output handling for workflow interactions, improving clarity and maintainability.
- Update tests to validate the new routing logic and agent behavior under various scenarios.

backend/tests/test_workflow_routing.py

@@ -0,0 +1,80 @@
+from __future__ import annotations
+
+import unittest
+
+from services.runtime_variables import DynamicVariableStore
+from services.workflow.models import LLMRouteResult, RouteStatus
+from services.workflow.routing import WorkflowEdgeEvaluator
+from services.workflow_engine import WorkflowEngine
+
+
+def routing_graph() -> dict:
+    return {
+        "specVersion": 3,
+        "settings": {},
+        "nodes": [
+            {"id": "start", "type": "start", "data": {}},
+            {"id": "agent", "type": "agent", "data": {"name": "Agent"}},
+            {"id": "matched", "type": "end", "data": {}},
+            {"id": "fallback", "type": "end", "data": {}},
+        ],
+        "edges": [
+            {
+                "id": "condition",
+                "source": "agent",
+                "target": "matched",
+                "data": {
+                    "mode": "llm",
+                    "priority": 10,
+                    "condition": "用户要求结束",
+                },
+            },
+            {
+                "id": "default",
+                "source": "agent",
+                "target": "fallback",
+                "data": {"mode": "always", "priority": 10},
+            },
+        ],
+    }
+
+
+class WorkflowEdgeEvaluatorTest(unittest.IsolatedAsyncioTestCase):
+    async def test_router_error_does_not_take_default_path(self):
+        class ErrorRouter:
+            async def select_edge(self, **_kwargs):
+                return LLMRouteResult(
+                    status=RouteStatus.ERROR,
+                    error="provider unavailable",
+                )
+
+        evaluator = WorkflowEdgeEvaluator(
+            WorkflowEngine(routing_graph()),
+            DynamicVariableStore({}),
+            lambda _node_id: ErrorRouter(),
+        )
+
+        decision = await evaluator.evaluate("agent")
+
+        self.assertEqual(decision.status, RouteStatus.ERROR)
+        self.assertIsNone(decision.edge)
+
+    async def test_explicit_no_match_takes_default_path(self):
+        class NoMatchRouter:
+            async def select_edge(self, **_kwargs):
+                return LLMRouteResult(status=RouteStatus.NO_MATCH)
+
+        evaluator = WorkflowEdgeEvaluator(
+            WorkflowEngine(routing_graph()),
+            DynamicVariableStore({}),
+            lambda _node_id: NoMatchRouter(),
+        )
+
+        decision = await evaluator.evaluate("agent")
+
+        self.assertEqual(decision.status, RouteStatus.MATCHED)
+        self.assertEqual(decision.edge["id"], "default")
+
+
+if __name__ == "__main__":
+    unittest.main()