feat(P1/P2): 完成TDD开发及P1/P2设计文档

## 设计文档
- multi_role_permission_design: 多角色权限设计 (CONDITIONAL GO)
- audit_log_enhancement_design: 审计日志增强 (CONDITIONAL GO)
- routing_strategy_template_design: 路由策略模板 (CONDITIONAL GO)
- sso_saml_technical_research: SSO/SAML调研 (CONDITIONAL GO)
- compliance_capability_package_design: 合规能力包设计 (CONDITIONAL GO)

## TDD开发成果
- IAM模块: supply-api/internal/iam/ (111个测试)
- 审计日志模块: supply-api/internal/audit/ (40+测试)
- 路由策略模块: gateway/internal/router/ (33+测试)
- 合规能力包: gateway/internal/compliance/ + scripts/ci/compliance/

## 规范文档
- parallel_agent_output_quality_standards: 并行Agent产出质量规范
- project_experience_summary: 项目经验总结 (v2)
- 2026-04-02-p1-p2-tdd-execution-plan: TDD执行计划

## 评审报告
- 5个CONDITIONAL GO设计文档评审报告
- fix_verification_report: 修复验证报告
- full_verification_report: 全面质量验证报告
- tdd_module_quality_verification: TDD模块质量验证
- tdd_execution_summary: TDD执行总结

依据: Superpowers执行框架 + TDD规范

gateway/internal/router/metrics/routing_metrics.go

@@ -0,0 +1,182 @@
+package metrics
+
+import (
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// RoutingMetrics 路由指标收集器 (M-008)
+type RoutingMetrics struct {
+	// 计数器
+	totalRequests    int64
+	totalTakeovers   int64
+	primaryTakeovers int64
+	fallbackTakeovers int64
+	noMarkCount      int64
+
+	// 按provider统计
+	providerStats map[string]*ProviderStat
+	providerMu    sync.RWMutex
+
+	// 按策略统计
+	strategyStats map[string]*StrategyStat
+	strategyMu   sync.RWMutex
+
+	// 时间窗口
+	windowStart time.Time
+}
+
+// ProviderStat Provider统计
+type ProviderStat struct {
+	Count      int64
+	LatencySum int64
+	Errors     int64
+}
+
+// StrategyStat 策略统计
+type StrategyStat struct {
+	Count       int64
+	Takeovers   int64
+	LatencySum  int64
+}
+
+// RoutingStats 路由统计
+type RoutingStats struct {
+	TotalRequests    int64
+	TotalTakeovers   int64
+	PrimaryTakeovers int64
+	FallbackTakeovers int64
+	NoMarkCount      int64
+	TakeoverRate     float64
+	M008Coverage     float64 // 路由标记覆盖率 >= 99.9%
+	ProviderStats    map[string]*ProviderStat
+	StrategyStats    map[string]*StrategyStat
+}
+
+// NewRoutingMetrics 创建路由指标收集器
+func NewRoutingMetrics() *RoutingMetrics {
+	return &RoutingMetrics{
+		providerStats: make(map[string]*ProviderStat),
+		strategyStats: make(map[string]*StrategyStat),
+		windowStart:   time.Now(),
+	}
+}
+
+// RecordTakeoverMark 记录接管标记
+// pathType: "primary" 或 "fallback"
+// strategy: 使用的策略名称
+func (m *RoutingMetrics) RecordTakeoverMark(provider string, tier int, pathType string, strategy string) {
+	atomic.AddInt64(&m.totalTakeovers, 1)
+
+	// 更新路径类型计数
+	switch pathType {
+	case "primary":
+		atomic.AddInt64(&m.primaryTakeovers, 1)
+	case "fallback":
+		atomic.AddInt64(&m.fallbackTakeovers, 1)
+	}
+
+	// 更新Provider统计
+	m.providerMu.Lock()
+	if _, ok := m.providerStats[provider]; !ok {
+		m.providerStats[provider] = &ProviderStat{}
+	}
+	m.providerStats[provider].Count++
+	m.providerMu.Unlock()
+
+	// 更新策略统计
+	m.strategyMu.Lock()
+	if _, ok := m.strategyStats[strategy]; !ok {
+		m.strategyStats[strategy] = &StrategyStat{}
+	}
+	m.strategyStats[strategy].Count++
+	m.strategyStats[strategy].Takeovers++
+	m.strategyMu.Unlock()
+}
+
+// RecordNoMark 记录未标记的请求（用于计算覆盖率）
+func (m *RoutingMetrics) RecordNoMark(reason string) {
+	atomic.AddInt64(&m.noMarkCount, 1)
+}
+
+// RecordRequest 记录请求
+func (m *RoutingMetrics) RecordRequest() {
+	atomic.AddInt64(&m.totalRequests, 1)
+}
+
+// GetStats 获取统计信息
+func (m *RoutingMetrics) GetStats() *RoutingStats {
+	total := atomic.LoadInt64(&m.totalRequests)
+	takeovers := atomic.LoadInt64(&m.totalTakeovers)
+	primary := atomic.LoadInt64(&m.primaryTakeovers)
+	fallback := atomic.LoadInt64(&m.fallbackTakeovers)
+	noMark := atomic.LoadInt64(&m.noMarkCount)
+
+	// 计算接管率 (有标记的请求 / 总请求)
+	var takeoverRate float64
+	if total > 0 {
+		takeoverRate = float64(takeovers) / float64(total) * 100
+	}
+
+	// 计算M-008覆盖率 (有标记的请求 / 总请求)
+	var coverage float64
+	if total > 0 {
+		coverage = float64(takeovers) / float64(total) * 100
+	}
+
+	// 复制Provider统计
+	m.providerMu.RLock()
+	providerStats := make(map[string]*ProviderStat)
+	for k, v := range m.providerStats {
+		providerStats[k] = &ProviderStat{
+			Count:      v.Count,
+			LatencySum: v.LatencySum,
+			Errors:     v.Errors,
+		}
+	}
+	m.providerMu.RUnlock()
+
+	// 复制策略统计
+	m.strategyMu.RLock()
+	strategyStats := make(map[string]*StrategyStat)
+	for k, v := range m.strategyStats {
+		strategyStats[k] = &StrategyStat{
+			Count:      v.Count,
+			Takeovers:  v.Takeovers,
+			LatencySum: v.LatencySum,
+		}
+	}
+	m.strategyMu.RUnlock()
+
+	return &RoutingStats{
+		TotalRequests:     total,
+		TotalTakeovers:    takeovers,
+		PrimaryTakeovers:  primary,
+		FallbackTakeovers: fallback,
+		NoMarkCount:       noMark,
+		TakeoverRate:      takeoverRate,
+		M008Coverage:      coverage,
+		ProviderStats:     providerStats,
+		StrategyStats:     strategyStats,
+	}
+}
+
+// Reset 重置统计
+func (m *RoutingMetrics) Reset() {
+	atomic.StoreInt64(&m.totalRequests, 0)
+	atomic.StoreInt64(&m.totalTakeovers, 0)
+	atomic.StoreInt64(&m.primaryTakeovers, 0)
+	atomic.StoreInt64(&m.fallbackTakeovers, 0)
+	atomic.StoreInt64(&m.noMarkCount, 0)
+
+	m.providerMu.Lock()
+	m.providerStats = make(map[string]*ProviderStat)
+	m.providerMu.Unlock()
+
+	m.strategyMu.Lock()
+	m.strategyStats = make(map[string]*StrategyStat)
+	m.strategyMu.Unlock()
+
+	m.windowStart = time.Now()
+}