feat: add workflow action outcomes and tracing

backend/services/workflow/output.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from typing import Any
+from uuid import uuid4
 
 from pipecat.frames.frames import OutputTransportMessageUrgentFrame, TTSSpeakFrame
 from pipecat.utils.time import time_now_iso8601
@@ -67,6 +68,29 @@ class WorkflowOutput:
         if node_id:
             await self.emit({"type": "node-active", "nodeId": node_id})
 
+    async def emit_trace(
+        self,
+        event: str,
+        *,
+        revision: str,
+        transition_id: int,
+        **details: Any,
+    ) -> None:
+        """Publish one ordered, machine-readable Workflow runtime event."""
+
+        await self.emit(
+            {
+                "type": "workflow-event",
+                "eventId": f"wfe_{uuid4().hex[:20]}",
+                "event": event,
+                "timestamp": time_now_iso8601(),
+                "sessionId": self._runtime.session_id,
+                "workflowRevision": revision,
+                "transitionId": transition_id,
+                **details,
+            }
+        )
+
     async def emit_variables(
         self,
         *,