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_v3.py

@@ -211,7 +211,7 @@ class WorkflowGraphTests(unittest.TestCase):
             "smart_turn",
         )
 
-    def test_start_agent_and_handoff_may_have_no_outgoing_edge(self):
+    def test_start_agent_action_and_handoff_may_have_no_outgoing_edge(self):
         terminal_graphs = [
             {
                 "specVersion": 3,
@@ -277,13 +277,47 @@ class WorkflowGraphTests(unittest.TestCase):
                 }
             ],
         }
+        self.assertEqual(validate_graph(action_without_exit), [])
+
+    def test_agent_cannot_have_only_one_default_path(self):
+        graph = {
+            "specVersion": 3,
+            "settings": {},
+            "nodes": [
+                {"id": "start", "type": "start", "data": {}},
+                {"id": "agent", "type": "agent", "data": {}},
+                {"id": "end", "type": "end", "data": {}},
+            ],
+            "edges": [
+                {
+                    "id": "begin",
+                    "source": "start",
+                    "target": "agent",
+                    "data": {"mode": "always", "priority": 0},
+                },
+                {
+                    "id": "leave",
+                    "source": "agent",
+                    "target": "end",
+                    "data": {"mode": "always", "priority": 0},
+                },
+            ],
+        }
+
         self.assertTrue(
             any(
-                "action 的出边不能少于 1" in error
-                for error in validate_graph(action_without_exit)
+                "Agent 节点 agent 不能只有默认路径" in error
+                for error in validate_graph(graph)
             )
         )
 
+        graph["edges"][1]["data"] = {
+            "mode": "llm",
+            "priority": 10,
+            "condition": "当前阶段已经完成",
+        }
+        self.assertEqual(validate_graph(graph), [])
+
     def test_all_source_nodes_allow_multiple_conditional_paths(self):
         expression = {
             "combinator": "and",
@@ -448,6 +482,41 @@ class WorkflowGraphTests(unittest.TestCase):
         self.assertNotIn("服务 王先生", custom_prompt)
         self.assertIn("处理订单", custom_prompt)
 
+    def test_missing_variable_only_matches_explicit_exists_rule(self):
+        engine = WorkflowEngine(valid_graph())
+        values = {}
+
+        self.assertFalse(
+            engine.expression_matches(
+                {
+                    "combinator": "and",
+                    "rules": [
+                        {
+                            "variable": "order_status",
+                            "operator": "neq",
+                            "value": "paid",
+                        }
+                    ],
+                },
+                values,
+            )
+        )
+        self.assertTrue(
+            engine.expression_matches(
+                {
+                    "combinator": "and",
+                    "rules": [
+                        {
+                            "variable": "order_status",
+                            "operator": "exists",
+                            "value": False,
+                        }
+                    ],
+                },
+                values,
+            )
+        )
+
 
 if __name__ == "__main__":
     unittest.main()