fix(acceptance): 物化验收任务的最终媒体

仅对已认证 Acceptance Run 强制下载并持久化 URL 型结果，确保集群外压测端能验证最终视频；普通生产任务继续遵循现有文件存储策略。压测器仅对 Gateway 自有地址做双入口重写，避免向第三方媒体域名泄露验收凭据。\n\n同时修复本地集群重复使用同一快照文件时的幂等复制失败。验证：Go 全量测试、go vet、gofmt、bash -n、ShellCheck 和 git diff --check 通过。

apps/api/internal/runner/upload.go

@@ -112,7 +112,7 @@ func mediaTaskNeedsPreUpstreamMaterializationSlot(modelType string) bool {
 	}
 }
 
-func (s *Service) uploadGeneratedAssets(ctx context.Context, taskID string, taskKind string, result map[string]any) (map[string]any, error) {
+func (s *Service) uploadGeneratedAssets(ctx context.Context, taskID string, taskKind string, acceptanceRunID string, result map[string]any) (map[string]any, error) {
 	data, _ := result["data"].([]any)
 	rawNeedsUpload := generatedRawValueHasInlineMedia(result["raw"], "", nil)
 	hasInlineBinary := TaskResultHasInlineBinary(result)
@@ -124,6 +124,11 @@ func (s *Service) uploadGeneratedAssets(ctx context.Context, taskID string, task
 	if err != nil {
 		return nil, &clients.ClientError{Code: "upload_config_failed", Message: err.Error(), Retryable: true}
 	}
+	// Acceptance runs must prove that a final URL returned by the protocol
+	// emulator can be persisted and consumed outside the cluster. Keep this
+	// override scoped to the authenticated run so normal production tasks retain
+	// the configured file-storage policy.
+	policy = generatedAssetUploadPolicyForAcceptanceRun(policy, acceptanceRunID)
 	if policy.LocalizeInlineMedia {
 		next, _, err := s.materializeLocalBinaryResult(ctx, taskID, result)
 		if err != nil {
@@ -260,6 +265,13 @@ func (s *Service) uploadGeneratedAssets(ctx context.Context, taskID string, task
 	return s.finalizeGeneratedAssets(ctx, taskID, taskKind, next, policy, channels, channelsLoaded, len(nextData))
 }
 
+func generatedAssetUploadPolicyForAcceptanceRun(policy generatedAssetUploadPolicy, acceptanceRunID string) generatedAssetUploadPolicy {
+	if strings.TrimSpace(acceptanceRunID) != "" {
+		policy.UploadURLMedia = true
+	}
+	return policy
+}
+
 func (s *Service) finalizeGeneratedAssets(
 	ctx context.Context,
 	taskID string,