fix(worker): 统一异步执行准入范围

Worker 执行阶段重建准入范围时遗漏 worker_capacity，导致已预留 River 槽的任务再次同步等待准入并占住执行槽。

调度、执行和候选切换统一复用 taskAdmissionScopes，确保异步任务始终携带同一全局 Worker 容量范围。

验证：Go 全量测试、runner race、go vet、迁移安全检查通过。

apps/api/internal/runner/admission.go

@@ -113,14 +113,10 @@ func (s *Service) buildTaskAdmissionPlan(ctx context.Context, task store.Gateway
 		if !available {
 			continue
 		}
-		scopes, groupID := s.admissionScopes(ctx, user, candidate)
+		scopes, groupID, scopeErr := s.taskAdmissionScopes(ctx, task, user, candidate)
-		if task.AsyncMode {
+		if scopeErr != nil {
-			scopes, err = s.withAsyncWorkerCapacityScope(ctx, scopes)
+			return taskAdmissionPlan{}, scopeErr
-			if err != nil {
-				return taskAdmissionPlan{}, err
-			}
 		}
-		scopes = acceptanceAdmissionScopes(task, scopes)
 		hasConcurrentLimit := false
 		for _, scope := range scopes {
 			if scope.ConcurrentLimit > 0 {
@@ -172,6 +168,23 @@ func (s *Service) withAsyncWorkerCapacityScope(ctx context.Context, scopes []sto
 	return out, nil
 }
 
+func (s *Service) taskAdmissionScopes(
+	ctx context.Context,
+	task store.GatewayTask,
+	user *auth.User,
+	candidate store.RuntimeModelCandidate,
+) ([]store.AdmissionScope, string, error) {
+	scopes, groupID := s.admissionScopes(ctx, user, candidate)
+	if task.AsyncMode {
+		var err error
+		scopes, err = s.withAsyncWorkerCapacityScope(ctx, scopes)
+		if err != nil {
+			return nil, "", err
+		}
+	}
+	return acceptanceAdmissionScopes(task, scopes), groupID, nil
+}
+
 func acceptanceAdmissionScopes(task store.GatewayTask, scopes []store.AdmissionScope) []store.AdmissionScope {
 	if task.RunMode != "acceptance" && task.RunMode != "acceptance_canary" {
 		return scopes
@@ -357,15 +370,10 @@ func (s *Service) ensureCandidateAdmission(
 	body map[string]any,
 	candidate store.RuntimeModelCandidate,
 ) (store.TaskAdmissionResult, bool, error) {
-	scopes, groupID := s.admissionScopes(ctx, user, candidate)
+	scopes, groupID, err := s.taskAdmissionScopes(ctx, task, user, candidate)
-	if task.AsyncMode {
+	if err != nil {
-		var err error
+		return store.TaskAdmissionResult{}, true, err
-		scopes, err = s.withAsyncWorkerCapacityScope(ctx, scopes)
-		if err != nil {
-			return store.TaskAdmissionResult{}, true, err
-		}
 	}
-	scopes = acceptanceAdmissionScopes(task, scopes)
 	hasConcurrentLimit := false
 	for _, scope := range scopes {
 		if scope.ConcurrentLimit > 0 {

apps/api/internal/runner/service.go

@@ -544,8 +544,10 @@ func (s *Service) executeWithToken(ctx context.Context, task store.GatewayTask,
 	var admittedLeases []store.ConcurrencyLease
 	admittedPlatformModelID := ""
 	if distributedAdmission && len(candidates) > 0 {
-		admissionScopes, groupID := s.admissionScopes(ctx, user, candidates[0])
+		admissionScopes, groupID, scopeErr := s.taskAdmissionScopes(ctx, task, user, candidates[0])
-		admissionScopes = acceptanceAdmissionScopes(task, admissionScopes)
+		if scopeErr != nil {
+			return Result{}, scopeErr
+		}
 		hasConcurrentLimit := false
 		for _, scope := range admissionScopes {
 			if scope.ConcurrentLimit > 0 {