feat(ai-core): mood state machine and affection level

- new emotion package: rule-based sentiment (positive/negative lexicon)
  drives mood transitions (开心/平静/难过) with 30min inactivity decay;
  affection 0-100 grows with positive interaction, with 初识→熟悉→信赖→
  羁绊 tiers
- pipeline records each user message and injects a mood line into the
  system prompt so the persona's tone follows her mood
- mood changes broadcast over WS; frontend shows a mood badge with
  affection tooltip; also handles the 'reminder' message type from the
  reminder scheduler
- tests: sentiment scoring, mood shift, affection bounds, prompt line,
  onChange callback

frontend/web/src/components/chat/ChatContainer.tsx

@@ -4,9 +4,14 @@ import { useWebSocket } from '../../hooks/useWebSocket'
 import MessageList from './MessageList'
 import ChatInput from './ChatInput'
 
+function moodEmoji(mood: string): string {
+  const map: Record<string, string> = { 开心: '😊', 平静: '😌', 难过: '😢', 害羞: '☺️', 感动: '🥹' }
+  return map[mood] || '😌'
+}
+
 export default function ChatContainer() {
   const { send } = useWebSocket()
-  const { messages, isStreaming, currentSessionId, inputText, setInput, addMessage, setStreaming } = useChatStore()
+  const { messages, isStreaming, currentSessionId, inputText, mood, setInput, addMessage, setStreaming } = useChatStore()
   const bottomRef = useRef<HTMLDivElement>(null)
 
   useEffect(() => {
@@ -34,7 +39,16 @@ export default function ChatContainer() {
   }
 
   return (
-    <div className="flex flex-col h-full">
+    <div className="flex flex-col h-full relative">
+      {/* Mood badge */}
+      {mood && (
+        <div className="absolute top-3 right-4 z-10 px-3 py-1 rounded-full text-xs border"
+          style={{ background: 'var(--mx-surface)', borderColor: 'var(--mx-outline)', color: 'var(--mx-text-dim)' }}
+          title={`好感度 ${mood.affection}/100`}>
+          {moodEmoji(mood.mood)} {mood.mood}
+        </div>
+      )}
+
       {/* Chat area */}
       <div className="flex-1 overflow-auto">
         <div className="max-w-2xl mx-auto px-4 py-6">