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/store/chatStore.ts

@@ -1,16 +1,24 @@
 import { create } from 'zustand'
 import type { Message, IotDevice } from '../types/chat'
 
+interface MoodState {
+  mood: string
+  intensity: number
+  affection: number
+}
+
 interface ChatState {
   messages: Message[]
   isStreaming: boolean
   currentSessionId: string | null
   iotDevices: IotDevice[]
   inputText: string
+  mood: MoodState | null
 
   setInput: (text: string) => void
   setSessionId: (id: string) => void
   setMessages: (msgs: Message[]) => void
+  setMood: (m: MoodState) => void
   addMessage: (msg: Message) => void
   appendToLast: (content: string) => void
   setStreaming: (v: boolean) => void
@@ -24,10 +32,12 @@ export const useChatStore = create<ChatState>((set, get) => ({
   currentSessionId: null,
   iotDevices: [],
   inputText: '',
+  mood: null,
 
   setInput: (text) => set({ inputText: text }),
   setSessionId: (id) => set({ currentSessionId: id }),
   setMessages: (msgs) => set({ messages: msgs }),
+  setMood: (m) => set({ mood: m }),
   setStreaming: (v) => set({ isStreaming: v }),
   setIotDevices: (d) => set({ iotDevices: d }),