feat: 优化情景切换功能

frontend/src/lib/i18n/en-US.ts

@@ -33,14 +33,19 @@ export const enUS: TranslationMap = {
   "scenario.choose": "Choose a scenario",
   "scenario.freeChat": "Free Chat",
   "scenario.freeChat.desc": "AI visual assistant, chat freely",
+  "scenario.freeChat.hint": "AI will act as a visual assistant to answer your questions",
   "scenario.interviewer": "Mock Interviewer",
   "scenario.interviewer.desc": "AI plays interviewer for practice",
+  "scenario.interviewer.hint": "AI will act as an interviewer, asking professional questions and providing feedback",
   "scenario.englishTeacher": "English Tutor",
   "scenario.englishTeacher.desc": "AI English tutor, corrects grammar",
+  "scenario.englishTeacher.hint": "AI will converse in English, correct grammar mistakes, and guide deeper conversations",
   "scenario.debate": "Debate Opponent",
   "scenario.debate.desc": "AI challenges your viewpoints",
+  "scenario.debate.hint": "AI will argue against your viewpoints using logic and evidence",
   "scenario.interpreter": "Interpreter",
   "scenario.interpreter.desc": "Real-time Chinese-English translation",
+  "scenario.interpreter.hint": "AI will translate your speech in real-time (Chinese-English), without explanations",
 
   // Video indicators
   "video.observing": "👁️ Observing",

frontend/src/lib/i18n/ja-JP.ts

@@ -33,14 +33,19 @@ export const jaJP: TranslationMap = {
   "scenario.choose": "シナリオを選択",
   "scenario.freeChat": "フリーチャット",
   "scenario.freeChat.desc": "AIビジュアルアシスタントと自由に会話",
+  "scenario.freeChat.hint": "AIがビジュアルアシスタントとしてあなたの質問に答えます",
   "scenario.interviewer": "模擬面接官",
   "scenario.interviewer.desc": "AIが面接官として模擬面接を実施",
+  "scenario.interviewer.hint": "AIが面接官として専門的な質問をし、フィードバックを提供します",
   "scenario.englishTeacher": "英語の先生",
   "scenario.englishTeacher.desc": "AI英語教師が文法を修正し会話を導く",
+  "scenario.englishTeacher.hint": "AIが英語で会話し、文法の誤りを修正して深い対話を導きます",
   "scenario.debate": "ディベート相手",
   "scenario.debate.desc": "AIがあなたの观点に反論し論理的思考を鍛える",
+  "scenario.debate.hint": "AIが反対の立場から論理と証拠であなたの观点に反論します",
   "scenario.interpreter": "同時通訳",
   "scenario.interpreter.desc": "リアルタイムで中日相互翻訳",
+  "scenario.interpreter.hint": "AIがあなたの発言をリアルタイムで翻訳します（中日相互翻訳、説明なし）",
 
   // Video indicators
   "video.observing": "👁️ 観察中",

frontend/src/lib/i18n/zh-CN.ts

@@ -33,14 +33,19 @@ export const zhCN: TranslationMap = {
   "scenario.choose": "选择对话情景",
   "scenario.freeChat": "自由对话",
   "scenario.freeChat.desc": "AI 视觉助手，自由聊天",
+  "scenario.freeChat.hint": "AI 会作为视觉助手回答你的问题",
   "scenario.interviewer": "模拟面试官",
   "scenario.interviewer.desc": "AI 扮演面试官，进行模拟面试",
+  "scenario.interviewer.hint": "AI 会扮演面试官，逐步提出专业问题并点评你的回答",
   "scenario.englishTeacher": "英语老师",
   "scenario.englishTeacher.desc": "AI 英语外教，纠正语法并引导对话",
+  "scenario.englishTeacher.hint": "AI 会用英语对话，纠正语法错误并引导深入交流",
   "scenario.debate": "辩论对手",
   "scenario.debate.desc": "AI 反驳你的观点，锻炼逻辑思维",
+  "scenario.debate.hint": "AI 会站在反方立场，用逻辑和证据反驳你的观点",
   "scenario.interpreter": "同声翻译",
   "scenario.interpreter.desc": "实时中英互译，口语化翻译",
+  "scenario.interpreter.hint": "AI 会实时翻译你的话（中英互译），无解释评论",
 
   // Video indicators
   "video.observing": "👁️ 观察中",