Collapse handoff turns in the transcript instead of streaming them

internal/agents/manager_test.go

@@ -587,6 +587,9 @@ func TestCompactCarriesHandoff(t *testing.T) {
 				t.Fatalf("handoff turn.ended %v: want handoff and no inbox summary", ev.Payload)
 			}
 		}
+		if ev.Kind == "user.message" && ev.Actor == "byre" && *ev.AgentSessionId == old.Id && ev.Payload["handoff"] != true {
+			t.Fatalf("handoff prompt %v: want handoff flag", ev.Payload)
+		}
 	}
 
 	sessions, err := e.store.ListSessions(e.ctx, e.task.Id)