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/services/workflow_router.py

@@ -15,6 +15,8 @@ from loguru import logger
 from models import AssistantConfig
 from openai import AsyncOpenAI
 
+from services.workflow.models import LLMRouteResult, RouteStatus
+
 
 STAY_ON_CURRENT_NODE = "workflow_stay_on_current_node"
 # Compatibility alias for callers saved before all source nodes supported LLM edges.
@@ -38,10 +40,10 @@ class WorkflowLLMRouter:
         variables: dict[str, Any],
         edge_name: Callable[[dict[str, Any]], str],
         edge_description: Callable[[dict[str, Any]], str],
-    ) -> str | None:
-        """Return an edge function name, STAY, or None when routing failed."""
+    ) -> LLMRouteResult:
+        """Return a typed match, no-match or technical error."""
         if not edges:
-            return STAY_ON_CURRENT_NODE
+            return LLMRouteResult(status=RouteStatus.NO_MATCH)
 
         names = {edge_name(edge) for edge in edges}
         stay_name = STAY_ON_CURRENT_NODE
@@ -116,16 +118,28 @@ class WorkflowLLMRouter:
             tool_calls = response.choices[0].message.tool_calls or []
             if not tool_calls:
                 logger.warning("Workflow 路由 LLM 未返回函数调用，留在当前节点")
-                return STAY_ON_CURRENT_NODE
+                return LLMRouteResult(
+                    status=RouteStatus.ERROR,
+                    error="路由模型没有返回函数调用",
+                )
             selected = str(tool_calls[0].function.name or "")
             if selected == stay_name:
-                return STAY_ON_CURRENT_NODE
+                return LLMRouteResult(status=RouteStatus.NO_MATCH)
             if selected not in names:
                 logger.warning(f"Workflow 路由 LLM 返回未知函数:{selected}")
-                return STAY_ON_CURRENT_NODE
-            return selected
+                return LLMRouteResult(
+                    status=RouteStatus.ERROR,
+                    error=f"路由模型返回未知函数:{selected}",
+                )
+            return LLMRouteResult(
+                status=RouteStatus.MATCHED,
+                function_name=selected,
+            )
         except Exception as exc:  # noqa: BLE001 - routing failure must not end the call
             logger.warning(f"Workflow LLM 边判断失败，留在当前节点:{exc}")
-            return None
+            return LLMRouteResult(
+                status=RouteStatus.ERROR,
+                error=f"大模型路由失败:{type(exc).__name__}",
+            )
         finally:
             await client.close()