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/node_specs.py

@@ -73,7 +73,7 @@ NODE_SPECS: list[dict[str, Any]] = [
         "icon": "Zap",
         "accent": "peach",
         "addable": True,
-        "constraints": {"minIncoming": 1, "minOutgoing": 1},
+        "constraints": {"minIncoming": 1, "minOutgoing": 0},
         "fields": [
             {"key": "name", "label": "节点名称", "type": "text", "default": "Action"},
         ],
@@ -352,18 +352,19 @@ def validate_graph(graph: dict[str, Any]) -> list[str]:
         if mode == "expression":
             expression_errors = _validate_expression(data.get("expression"))
             errors.extend(f"边 {edge_id}:{item}" for item in expression_errors)
-        try:
-            priority = int(data.get("priority", 10))
-        except (TypeError, ValueError):
-            errors.append(f"边 {edge_id} 的优先级必须是整数")
-            priority = 10
-        if priority in priorities[source_id]:
-            errors.append(f"节点 {source_id} 的出边优先级不能重复:{priority}")
-        priorities[source_id].add(priority)
         if mode == "always":
             always_counts[source_id] += 1
             if always_counts[source_id] > 1:
                 errors.append(f"节点 {source_id} 最多只能有一条默认路径")
+        else:
+            try:
+                priority = int(data.get("priority", 10))
+            except (TypeError, ValueError):
+                errors.append(f"边 {edge_id} 的优先级必须是整数")
+                priority = 10
+            if priority in priorities[source_id]:
+                errors.append(f"节点 {source_id} 的条件边优先级不能重复:{priority}")
+            priorities[source_id].add(priority)
         incoming[target_id] += 1
         outgoing[source_id] += 1
         adj[source_id].append(target_id)
@@ -387,6 +388,15 @@ def validate_graph(graph: dict[str, Any]) -> list[str]:
                 errors.append(f"节点 {node_id} 的{label}不能少于 {lo}")
             if hi is not None and actual > hi:
                 errors.append(f"节点 {node_id} 的{label}不能多于 {hi}")
+        if (
+            node.get("type") == "agent"
+            and outgoing[node_id] == 1
+            and always_counts[node_id] == 1
+        ):
+            errors.append(
+                f"Agent 节点 {node_id} 不能只有默认路径；"
+                "请改为条件路径，或删除该路径以持续对话"
+            )
     start_id = next(
         (node_id for node_id, node in node_by_id.items() if node.get("type") == "start"),
         None,