feat(ui): introduce each teacher with an individual welcome bubble

tests/e2e/fixtures/teacher-preview-layout.tsx

@@ -18,6 +18,8 @@ export function Layout() {
   const [refreshing, setRefreshing] = useState(false);
   const [refreshStatus, setRefreshStatus] = useState<'idle' | 'success' | 'error'>('idle');
   const [selected, setSelected] = useState(0);
+  const welcomeMode = new URLSearchParams(location.search).has('welcomes');
+  const [dismissed, setDismissed] = useState<string[]>([]);
   const agents = Array.from({ length: count }, (_, index) => ({
     teacher_id: `agent-${index}`, version: index + 1, is_default: index === 0,
     definition: { config_id: `agent-${index}`, name: `智能体${index + 1}`, avatar_id: 'avatar-06',
@@ -27,8 +29,11 @@ export function Layout() {
   const companion = {
     agents, unreadAgentIds: [], selectedAgent: agents[selected],
     definition: agents[selected]?.definition ?? { name: '编程老师', avatar_id: 'avatar-06' },
-    invitation: visible ? { response: long ? '你刚才说想做一个宠物游戏。我们一起想想，什么样的小动作，会让你愿意一直陪它玩下去？可以先挑一个最想试的想法。' : '有什么编程问题想一起讨论？' } : null,
+    invitation: !welcomeMode && visible ? { response: long ? '你刚才说想做一个宠物游戏。我们一起想想，什么样的小动作，会让你愿意一直陪它玩下去？可以先挑一个最想试的想法。' : '有什么编程问题想一起讨论？' } : null,
     welcome: null, enabled: true, loading: false, checking: false, error: null,
+    welcomes: welcomeMode && !open ? agents.flatMap((agent, index) => dismissed.includes(agent.teacher_id) ? [] : [{ agentId: agent.teacher_id, definition: agent.definition, text: agent.definition.description, tone: index % 3 }]) : [],
+    dismissWelcome: (id: string) => setDismissed(ids => [...new Set([...ids, id])]),
+    dismissWelcomes: () => setDismissed(agents.map(agent => agent.teacher_id)),
     refreshing, refreshStatus,
     refresh: async () => {
       setRefreshing(true);