fix: show and dismiss teacher introductions as one group

src/pages/Chat/TeacherCompanion.tsx

@@ -25,7 +25,7 @@ export function TeacherCompanion({ companion, open, onOpen, onToggle, bubbleRef,
   const agents = companion.selectedAgent && !companion.agents.some((item) => item.teacher_id === activeId)
     ? [...companion.agents, companion.selectedAgent] : companion.agents;
   const viewConversation = () => { companion.dismiss(); onOpen(); };
-  const meetTeacher = (agentId: string) => { setIntroductionId(null); companion.dismissWelcome(agentId); onOpen(agentId); };
+  const meetTeacher = (agentId: string) => { setIntroductionId(null); companion.dismissWelcomes(); onOpen(agentId); };
   const status = loading ? '正在连接智能体…'
     : checking ? '智能体在看看你最近的进展…'
     : error || (!enabled ? '智能体暂未开放，仍可查看以往讨论' : open ? '我们慢慢聊，想到什么都可以说' : '点我聊聊，想到什么都可以说');
@@ -74,7 +74,7 @@ export function TeacherCompanion({ companion, open, onOpen, onToggle, bubbleRef,
                 <span className="teacher-welcome-text" title={item.text}>{item.text}</span>
                 <span className="teacher-welcome-action">和我聊聊 <ArrowUpRight aria-hidden="true" className="h-3 w-3" /></span>
               </button>
-              <button type="button" className="teacher-welcome-dismiss" aria-label={`收起${item.definition.name}的介绍`} onClick={() => companion.dismissWelcome(item.agentId)}>
+              <button type="button" className="teacher-welcome-dismiss" aria-label={`收起全部老师介绍（${item.definition.name}）`} onClick={() => companion.dismissWelcomes()}>
                 <X className="h-3.5 w-3.5" aria-hidden="true" />
               </button>
             </div>