feat(chat): host-style memoir prompts and strip parenthetical stage directions

- Add strip_parenthetical_asides_for_chat in reply pipeline before [SPLIT]
- Expand output_rules bans (performance parens) and voice as warm host
- Refocus opening/guided prompts on pulling conversation toward memoir oral history
- Align interview opening fallbacks with memoir-first tone
- Add unit tests for parenthetical stripping

api/app/agents/chat/interview_agent.py

@@ -257,7 +257,7 @@ class InterviewAgent:
     ) -> List[str]:
         """生成空对话开场白，不持久化（由 Orchestrator 负责）"""
         if not self.llm:
-            return ["你好呀～ 又见面了，今天有没有哪段回忆或近况想聊聊？"]
+            return ["你好呀～ 又见面了。今天想从人生里哪一小段回忆开始聊聊？"]
         try:
             empty_slots = memoir_state.prompt_empty_slots_for_current_stage()
             empty_slots_readable = [SLOT_NAME_MAP.get(s, s) for s in empty_slots]
@@ -343,8 +343,8 @@ class InterviewAgent:
             segments = out if out else [response_text.strip()[:max_chars]]
             return nonempty_segments_or_fallback(
                 segments,
-                fallback="你好呀～ 又见面了，最近有没有什么事想跟我说说？",
+                fallback="你好呀～ 又见面了。今天想从人生里哪一小段回忆开始聊聊？",
             )
         except Exception as e:
             logger.error("生成开场白失败: {}", e, exc_info=True)
-            return ["你好呀～ 又见面了，最近有没有什么事想跟我说说？"]
+            return ["你好呀～ 又见面了。今天想从人生里哪一小段回忆开始聊聊？"]