fix(acceptance): 隔离控制面抖动与租约瞬态故障

线上 P24 验收暴露出高频 kubectl exec 放大 K3s API 压力、门禁查询挤占关键连接池，以及 PostgreSQL 锁超时被误判为租约所有权丢失。

本次合并验收身份查询、在租约有效期内重试瞬态续期错误、修复人工审核残留 attempt，并增加滚动后 etcd 稳定窗口、节点直连指标和双站独立报告。

验证：Go 全量测试、go vet、聚焦 race、gofmt、迁移安全检查、bash -n、ShellCheck、manual release test。

apps/api/internal/runner/execution_lease.go

@@ -11,24 +11,37 @@ import (
 const (
 	taskExecutionLeaseTTL      = 5 * time.Minute
 	taskExecutionRenewInterval = 30 * time.Second
+	leaseRenewalRetryInterval  = 2 * time.Second
 )
 
 func (s *Service) renewTaskExecutionLease(ctx context.Context, cancel context.CancelFunc, taskID string, executionToken string) {
-	ticker := time.NewTicker(taskExecutionRenewInterval)
-	defer ticker.Stop()
+	timer := time.NewTimer(taskExecutionRenewInterval)
+	defer timer.Stop()
+	leaseDeadline := time.Now().Add(taskExecutionLeaseTTL)
 	for {
 		select {
 		case <-ctx.Done():
 			return
-		case <-ticker.C:
+		case <-timer.C:
 			if err := s.coordinationStore.RenewTaskExecutionLease(ctx, taskID, executionToken, taskExecutionLeaseTTL); err != nil {
 				if errors.Is(err, store.ErrTaskExecutionFinished) {
 					return
 				}
-				s.logger.Warn("task execution lease lost", "taskID", taskID, "error_category", "task_execution_lease_lost")
-				cancel()
-				return
+				if taskExecutionLeaseRenewalIsFatal(err, time.Now(), leaseDeadline) {
+					s.logger.Warn("task execution lease lost", "taskID", taskID, "error_category", "task_execution_lease_lost", "error", err)
+					cancel()
+					return
+				}
+				s.logger.Warn("task execution lease renewal failed; retrying before lease expiry", "taskID", taskID, "error_category", "task_execution_lease_renewal_transient", "error", err)
+				timer.Reset(leaseRenewalRetryInterval)
+				continue
 			}
+			leaseDeadline = time.Now().Add(taskExecutionLeaseTTL)
+			timer.Reset(taskExecutionRenewInterval)
 		}
 	}
 }
+
+func taskExecutionLeaseRenewalIsFatal(err error, now time.Time, leaseDeadline time.Time) bool {
+	return errors.Is(err, store.ErrTaskExecutionLeaseLost) || !now.Before(leaseDeadline)
+}