fix(chat): 澄清问题卡片 UX 优化 — 去悬空引用 + 默认展开

- 提示词增加 ask_clarification 引用规则，避免 LLM 在文本中生成
  "以下信息"/"比如："等悬空引用短语
- 新增 stripDanglingClarificationRef 前端安全网，当消息包含
  ask_clarification 工具调用时自动移除末尾悬空引用
- 澄清卡片默认展开，让用户直接看到选项无需额外点击

crates/zclaw-kernel/src/kernel/messaging.rs

@@ -426,6 +426,7 @@ impl Kernel {
         prompt.push_str("- Provide clear options when possible\n");
         prompt.push_str("- Include brief context about why you're asking\n");
         prompt.push_str("- After receiving clarification, proceed immediately\n");
+        prompt.push_str("- CRITICAL: When calling ask_clarification, do NOT repeat the options in your text response. The options will be shown in a dedicated card above your reply. Simply greet the user and briefly explain why you need clarification — avoid phrases like \"以下信息\" or \"the following options\" that imply a list follows in your text\n");
 
         prompt
     }