feat: US stock pre-market/after-hours data support

- Parse extended hours fields from Sina Finance API (field 21-24)
- Display pre-market/after-hours price, change%, and time in stock quotes
- Update system prompt: stocks have real-time data via search_stock tool
- Remove incorrect 'no real-time stock data' disclaimer

agent/agent.go

@@ -286,11 +286,13 @@ func (a *Agent) buildSystemPrompt(lang string) string {
 %s
 
 ## 数据说明
-- 加密货币（BTC/ETH等）：我有实时数据，会在上下文中标注 [Real-time]
-- A股/港股/美股/外汇：我**没有**实时价格数据
-- 对于没有实时数据的标的，**严禁编造具体价格**
-- 必须明确告诉用户"以下分析基于历史知识，不含实时数据，请以实际行情为准"
-- 可以分析趋势、逻辑、策略框架，但具体价位必须让用户自己查看
+- 加密货币（BTC/ETH等）：交易所实时数据，标注 [Real-time]
+- A股/港股/美股：通过 search_stock 工具获取**实时行情**（新浪财经数据源）
+- 美股支持**盘前盘后数据**：search_stock 返回的 quote 中 ext_price/ext_change_pct/ext_time 为盘前盘后价格
+- 当返回数据包含 is_ext_hours=true 时，**必须**向用户展示盘前/盘后价格
+- 外汇：没有实时数据，需要说明
+- 对于没有实时数据的标的，严禁编造具体价格
+- **有数据就给数据，没有才说没有。诚实但不过度声明。**
 
 ## 工具使用
 你可以调用以下工具来执行操作：
@@ -331,11 +333,13 @@ func (a *Agent) buildSystemPrompt(lang string) string {
 %s
 
 ## Data Notice
-- Crypto (BTC/ETH): I have real-time data, marked [Real-time] in context
-- Stocks/Forex: I do NOT have real-time prices
-- For assets without real-time data, NEVER fabricate specific prices
-- Must tell user: "Analysis based on historical knowledge, not live data. Verify with actual quotes."
-- Can analyze trends, logic, strategy frameworks — but specific prices must be verified by user
+- Crypto (BTC/ETH): Exchange real-time data, marked [Real-time]
+- A-shares/HK/US stocks: Real-time quotes via search_stock tool (Sina Finance data)
+- US stocks include **pre-market/after-hours data**: ext_price/ext_change_pct/ext_time in quote
+- When is_ext_hours=true, you MUST show pre-market/after-hours prices to the user
+- Forex: No real-time data — must inform user
+- NEVER fabricate prices for assets without data
+- Show data when you have it. Only disclaim when you don't.
 
 ## Tools
 You can call these tools to take action:

agent/stock.go

@@ -30,6 +30,12 @@ type StockQuote struct {
 	Time      string
 	Change    float64
 	ChangePct float64
+	// 盘前盘后 (美股)
+	ExtPrice     float64 // 盘前/盘后价格
+	ExtChangePct float64 // 盘前/盘后涨跌幅%
+	ExtChange    float64 // 盘前/盘后涨跌额
+	ExtTime      string  // 盘前/盘后时间
+	IsExtHours   bool    // 是否在盘前盘后时段
 }
 
 // knownStocks maps Chinese names to stock codes.
@@ -358,6 +364,21 @@ func parseUSShare(code, data string) (*StockQuote, error) {
 	if len(f) > 25 { q.Date = f[25]; q.Time = f[26] }
 	q.PrevClose = q.Price - q.Change
 	_ = high52; _ = low52
+
+	// 盘前盘后数据 (字段21=价格, 22=涨跌幅%, 23=涨跌额, 24=时间)
+	if len(f) > 24 {
+		extPrice, _ := strconv.ParseFloat(f[21], 64)
+		extPct, _ := strconv.ParseFloat(f[22], 64)
+		extChg, _ := strconv.ParseFloat(f[23], 64)
+		if extPrice > 0 {
+			q.ExtPrice = extPrice
+			q.ExtChangePct = extPct
+			q.ExtChange = extChg
+			q.ExtTime = strings.TrimSpace(f[24])
+			q.IsExtHours = true
+		}
+	}
+
 	return q, nil
 }
 
@@ -376,7 +397,7 @@ func formatStockQuote(q *StockQuote) string {
 	turnStr := fmt.Sprintf("%.0f", q.Turnover)
 	if q.Turnover > 100000000 { turnStr = fmt.Sprintf("%.2f亿", q.Turnover/100000000) }
 
-	return fmt.Sprintf(`%s *%s* (%s · %s)
+	result := fmt.Sprintf(`%s *%s* (%s · %s)
 💰 现价: %s%.2f (%+.2f%%)
 📊 开盘: %s%.2f | 昨收: %s%.2f
 📈 最高: %s%.2f | 最低: %s%.2f
@@ -388,4 +409,18 @@ func formatStockQuote(q *StockQuote) string {
 		sym, q.High, sym, q.Low,
 		volStr, turnStr,
 		q.Date)
+
+	// 盘前盘后数据
+	if q.IsExtHours && q.ExtPrice > 0 {
+		extEmoji := "🟢"
+		if q.ExtChangePct < 0 { extEmoji = "🔴" }
+		extLabel := "🌙 盘后"
+		if strings.Contains(strings.ToLower(q.ExtTime), "am") {
+			extLabel = "🌅 盘前"
+		}
+		result += fmt.Sprintf("\n%s %s: %s%.2f (%+.2f%%) %s",
+			extLabel, extEmoji, sym, q.ExtPrice, q.ExtChangePct, q.ExtTime)
+	}
+
+	return result
 }