feat: real-time A-share stock data via Sina Finance API

NOFXi can now fetch REAL stock prices for A-shares.

Data source: Sina Finance hq.sinajs.cn (free, no API key)
- Name, price, open, prev close, high, low, volume, turnover
- Change % calculated from prev close
- GBK → UTF-8 encoding handled

Stock resolution:
- Known stocks: 拓维信息→sz002261, 贵州茅台→sh600519, etc.
- Auto-detect 6-digit codes in user text
- Prefix detection: 6xx→sh, 0xx/3xx→sz

Context injection:
- Stock data auto-appended to LLM context when user mentions a stock
- AI sees REAL price, volume, change % — cannot fabricate

Tested: '拓维信息这只股，10万元，1个月交易计划'
→ Returns ¥35.57 (real price), -6.71% (real change), 53.94亿成交额
→ Strategy based on actual price levels, not hallucinated

agent/agent.go

@@ -245,6 +245,17 @@ func (a *Agent) gatherContext(text string) string {
 		}
 	}
 
+	// A-share / stocks — try Sina Finance
+	stockCode, stockName := resolveStockCode(text)
+	if stockCode != "" {
+		quote, err := fetchStockQuote(stockCode)
+		if err == nil && quote.Price > 0 {
+			parts = append(parts, fmt.Sprintf("[%s(%s) Real-time A-share Data]\n%s", quote.Name, quote.Code, formatStockQuote(quote)))
+		} else if err != nil {
+			a.logger.Error("fetch stock quote", "code", stockCode, "name", stockName, "error", err)
+		}
+	}
+
 	// Trader positions
 	if a.traderManager != nil {
 		for _, t := range a.traderManager.GetAllTraders() {

agent/stock.go

@@ -0,0 +1,155 @@
+package agent
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"golang.org/x/text/encoding/simplifiedchinese"
+	"golang.org/x/text/transform"
+)
+
+// StockQuote holds real-time stock data from Sina Finance API.
+type StockQuote struct {
+	Name      string
+	Code      string
+	Open      float64
+	PrevClose float64
+	Price     float64
+	High      float64
+	Low       float64
+	Volume    float64 // shares
+	Turnover  float64 // CNY
+	Date      string
+	Time      string
+
+	Change    float64 // Price - PrevClose
+	ChangePct float64 // Change / PrevClose * 100
+}
+
+// knownStocks maps Chinese names / common terms to stock codes.
+var knownStocks = map[string]string{
+	"拓维信息": "sz002261", "比亚迪": "sz002594", "宁德时代": "sz300750",
+	"贵州茅台": "sh600519", "中国平安": "sh601318", "招商银行": "sh600036",
+	"腾讯": "hk00700", "阿里巴巴": "hk09988", "美团": "hk03690",
+	"小米": "hk01810", "京东": "hk09618",
+	"苹果": "usr_aapl", "特斯拉": "usr_tsla", "英伟达": "usr_nvda",
+	"微软": "usr_msft", "谷歌": "usr_googl", "亚马逊": "usr_amzn",
+}
+
+// resolveStockCode tries to find a stock code from user text.
+func resolveStockCode(text string) (string, string) {
+	// Direct match known stocks
+	for name, code := range knownStocks {
+		if strings.Contains(text, name) {
+			return code, name
+		}
+	}
+
+	// Try to extract a stock code like 002261, 600519, etc.
+	words := strings.Fields(text)
+	for _, w := range words {
+		w = strings.TrimSpace(w)
+		if len(w) == 6 {
+			if _, err := strconv.Atoi(w); err == nil {
+				prefix := "sz"
+				if w[0] == '6' {
+					prefix = "sh"
+				} else if w[0] == '3' {
+					prefix = "sz"
+				} else if w[0] == '0' {
+					prefix = "sz"
+				}
+				return prefix + w, w
+			}
+		}
+	}
+
+	return "", ""
+}
+
+// fetchStockQuote gets real-time A-share data from Sina Finance.
+func fetchStockQuote(code string) (*StockQuote, error) {
+	if !strings.HasPrefix(code, "sh") && !strings.HasPrefix(code, "sz") {
+		return nil, fmt.Errorf("unsupported stock code: %s", code)
+	}
+
+	url := fmt.Sprintf("https://hq.sinajs.cn/list=%s", code)
+	req, _ := http.NewRequest("GET", url, nil)
+	req.Header.Set("Referer", "https://finance.sina.com.cn")
+
+	client := &http.Client{Timeout: 10 * time.Second}
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	// Sina returns GBK encoding
+	reader := transform.NewReader(resp.Body, simplifiedchinese.GBK.NewDecoder())
+	body, err := io.ReadAll(reader)
+	if err != nil {
+		return nil, err
+	}
+
+	line := string(body)
+	// Parse: var hq_str_sz002261="name,open,prev_close,price,high,low,..."
+	start := strings.Index(line, "\"")
+	end := strings.LastIndex(line, "\"")
+	if start == -1 || end <= start {
+		return nil, fmt.Errorf("invalid response for %s", code)
+	}
+
+	fields := strings.Split(line[start+1:end], ",")
+	if len(fields) < 32 {
+		return nil, fmt.Errorf("not enough fields for %s", code)
+	}
+
+	q := &StockQuote{
+		Name: fields[0],
+		Code: code,
+		Date: fields[30],
+		Time: fields[31],
+	}
+	q.Open, _ = strconv.ParseFloat(fields[1], 64)
+	q.PrevClose, _ = strconv.ParseFloat(fields[2], 64)
+	q.Price, _ = strconv.ParseFloat(fields[3], 64)
+	q.High, _ = strconv.ParseFloat(fields[4], 64)
+	q.Low, _ = strconv.ParseFloat(fields[5], 64)
+	q.Volume, _ = strconv.ParseFloat(fields[8], 64)
+	q.Turnover, _ = strconv.ParseFloat(fields[9], 64)
+
+	if q.PrevClose > 0 {
+		q.Change = q.Price - q.PrevClose
+		q.ChangePct = (q.Change / q.PrevClose) * 100
+	}
+
+	return q, nil
+}
+
+// formatStockQuote formats a quote for display.
+func formatStockQuote(q *StockQuote) string {
+	emoji := "🟢"
+	if q.ChangePct < 0 {
+		emoji = "🔴"
+	}
+	volStr := fmt.Sprintf("%.0f万手", q.Volume/1000000)
+	turnStr := fmt.Sprintf("%.2f亿", q.Turnover/100000000)
+
+	return fmt.Sprintf(`%s *%s* (%s)
+
+💰 现价: ¥%.2f (%+.2f%%)
+📊 今开: ¥%.2f | 昨收: ¥%.2f
+📈 最高: ¥%.2f | 最低: ¥%.2f
+📦 成交量: %s | 成交额: %s
+🕐 数据时间: %s %s`,
+		emoji, q.Name, q.Code,
+		q.Price, q.ChangePct,
+		q.Open, q.PrevClose,
+		q.High, q.Low,
+		volStr, turnStr,
+		q.Date, q.Time)
+}