perf(decision): precompile regex patterns for performance

## Changes
- Move all regex patterns to global precompiled variables
- Reduces regex compilation overhead from O(n) to O(1)
- Matches z-dev's performance optimization

## Modified Patterns
- reJSONFence: Match ```json code blocks
- reJSONArray: Match JSON arrays
- reArrayHead: Validate array start
- reArrayOpenSpace: Compact array formatting
- reInvisibleRunes: Remove zero-width characters

## Performance Impact
- Regex compilation now happens once at startup
- Eliminates repeated compilation in extractDecisions() (called every decision cycle)
- Expected performance improvement: ~5-10% in JSON parsing

## Safety
✅ All regex patterns remain unchanged (only moved to global scope)
✅ Compilation successful
✅ Maintains same functionality as before

decision/engine.go

@@ -12,6 +12,17 @@ import (
 	"time"
 )
 
+// 预编译正则表达式（性能优化：避免每次调用时重新编译）
+var (
+	// ✅ 安全的正則：精確匹配 ```json 代碼塊
+	// 使用反引號 + 拼接避免轉義問題
+	reJSONFence      = regexp.MustCompile(`(?is)` + "```json\\s*(\\[\\s*\\{.*?\\}\\s*\\])\\s*```")
+	reJSONArray      = regexp.MustCompile(`(?is)\[\s*\{.*?\}\s*\]`)
+	reArrayHead      = regexp.MustCompile(`^\[\s*\{`)
+	reArrayOpenSpace = regexp.MustCompile(`^\[\s+\{`)
+	reInvisibleRunes = regexp.MustCompile(`[\u200B\u200C\u200D\uFEFF]`)
+)
+
 // PositionInfo 持仓信息
 type PositionInfo struct {
 	Symbol           string  `json:"symbol"`
@@ -461,8 +472,7 @@ func extractDecisions(response string) ([]Decision, error) {
 	s = fixMissingQuotes(s)
 
 	// 1) 优先从 ```json 代码块中提取
-	reFence := regexp.MustCompile(`(?is)` + "```json\\s*(\\[\\s*\\{.*?\\}\\s*\\])\\s*```")
+	if m := reJSONFence.FindStringSubmatch(s); m != nil && len(m) > 1 {
-	if m := reFence.FindStringSubmatch(s); m != nil && len(m) > 1 {
 		jsonContent := strings.TrimSpace(m[1])
 		jsonContent = compactArrayOpen(jsonContent) // 把 "[ {" 规整为 "[{"
 		jsonContent = fixMissingQuotes(jsonContent) // 二次修復（防止 regex 提取後還有全角）
@@ -478,8 +488,7 @@ func extractDecisions(response string) ([]Decision, error) {
 
 	// 2) 退而求其次：全文寻找首个对象数组
 	// 注意：此時 s 已經過 fixMissingQuotes()，全角字符已轉換為半角
-	reArray := regexp.MustCompile(`(?is)\[\s*\{.*?\}\s*\]`)
+	jsonContent := strings.TrimSpace(reJSONArray.FindString(s))
-	jsonContent := strings.TrimSpace(reArray.FindString(s))
 	if jsonContent == "" {
 		return nil, fmt.Errorf("无法找到JSON数组起始（已嘗試修復全角字符）\n原始響應前200字符: %s", s[:min(200, len(s))])
 	}
@@ -536,8 +545,7 @@ func validateJSONFormat(jsonStr string) error {
 	trimmed := strings.TrimSpace(jsonStr)
 
 	// 允许 [ 和 { 之间存在任意空白（含零宽）
-	reHead := regexp.MustCompile(`^\[\s*\{`)
+	if !reArrayHead.MatchString(trimmed) {
-	if !reHead.MatchString(trimmed) {
 		// 检查是否是纯数字/范围数组（常见错误）
 		if strings.HasPrefix(trimmed, "[") && !strings.Contains(trimmed[:min(20, len(trimmed))], "{") {
 			return fmt.Errorf("不是有效的决策数组（必须包含对象 {}），实际内容: %s", trimmed[:min(50, len(trimmed))])
@@ -575,14 +583,12 @@ func min(a, b int) int {
 
 // removeInvisibleRunes 去除零宽字符和 BOM，避免肉眼看不见的前缀破坏校验
 func removeInvisibleRunes(s string) string {
-	re := regexp.MustCompile(`[\u200B\u200C\u200D\uFEFF]`)
+	return reInvisibleRunes.ReplaceAllString(s, "")
-	return re.ReplaceAllString(s, "")
 }
 
 // compactArrayOpen 规整开头的 "[ {" → "[{"
 func compactArrayOpen(s string) string {
-	re := regexp.MustCompile(`^\[\s+\{`)
+	return reArrayOpenSpace.ReplaceAllString(strings.TrimSpace(s), "[{")
-	return re.ReplaceAllString(strings.TrimSpace(s), "[{")
 }
 
 // validateDecisions 验证所有决策（需要账户信息和杠杆配置）