refactor: dedupe agent and reply runtimes

src/agents/pi-embedded-subscribe.e2e-harness.ts

@@ -182,6 +182,16 @@ export function emitAssistantLifecycleErrorAndEnd(params: {
   params.emit({ type: "agent_end" });
 }
 
+export function createReasoningFinalAnswerMessage(): AssistantMessage {
+  return {
+    role: "assistant",
+    content: [
+      { type: "thinking", thinking: "Because it helps" },
+      { type: "text", text: "Final answer" },
+    ],
+  } as AssistantMessage;
+}
+
 type LifecycleErrorAgentEvent = {
   stream?: unknown;
   data?: {