feat: add workflow action outcomes and tracing

backend/services/workflow/models.py

@@ -27,6 +27,65 @@ class RouteStatus(StrEnum):
     ERROR = "error"
 
 
+class ActionStatus(StrEnum):
+    """Stable Action outcomes used by routing and future debug tooling."""
+
+    SUCCESS = "success"
+    FAILURE = "failure"
+    CANCELLED = "cancelled"
+
+
+@dataclass(frozen=True)
+class ActionError:
+    """Machine-readable failure details without losing the operator message."""
+
+    code: str
+    message: str
+    retryable: bool = False
+
+
+@dataclass(frozen=True)
+class ActionOutcome:
+    """One completed Action invocation.
+
+    ``result`` remains an in-memory value because a tool response may contain
+    private business data. Trace events publish only its shape and variable
+    names, never the raw response.
+    """
+
+    invocation_id: str
+    status: ActionStatus
+    duration_ms: int
+    result: dict[str, Any] | None = None
+    updated_variables: tuple[str, ...] = ()
+    error: ActionError | None = None
+
+    @property
+    def should_route(self) -> bool:
+        """Cancellation is a lifecycle outcome, not a failure branch."""
+
+        return self.status != ActionStatus.CANCELLED
+
+    def trace_payload(self) -> dict[str, Any]:
+        """Return a persistence-safe summary of the execution result."""
+
+        payload: dict[str, Any] = {
+            "invocationId": self.invocation_id,
+            "status": self.status.value,
+            "durationMs": self.duration_ms,
+            "updatedVariables": list(self.updated_variables),
+        }
+        if self.result is not None:
+            payload["resultKeys"] = sorted(str(key) for key in self.result)
+        if self.error is not None:
+            payload["error"] = {
+                "code": self.error.code,
+                "message": self.error.message,
+                "retryable": self.error.retryable,
+            }
+        return payload
+
+
 @dataclass(frozen=True)
 class UserTurn:
     """One committed user turn that may cross automatic Workflow nodes."""
@@ -89,4 +148,3 @@ class EdgeEvaluation:
     status: RouteStatus
     edge: dict[str, Any] | None = None
     error: str | None = None
-