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_test.go

@@ -290,6 +290,17 @@ func TestGeneratedAssetUploadPolicyFromName(t *testing.T) {
 	}
 }
 
+func TestAcceptanceRunForcesURLMaterializationOnlyForAcceptanceTask(t *testing.T) {
+	configured := generatedAssetUploadPolicy{UploadInlineMedia: true}
+	if got := generatedAssetUploadPolicyForAcceptanceRun(configured, ""); got.UploadURLMedia {
+		t.Fatal("ordinary task unexpectedly enabled URL materialization")
+	}
+	got := generatedAssetUploadPolicyForAcceptanceRun(configured, "acceptance-run-id")
+	if !got.UploadInlineMedia || !got.UploadURLMedia {
+		t.Fatalf("acceptance policy=%+v", got)
+	}
+}
+
 func TestFinalizeGeneratedAssetsUploadsNestedInlineBinaryUnderDefaultPolicy(t *testing.T) {
 	storageDir := t.TempDir()
 	service := &Service{cfg: config.Config{LocalGeneratedStorageDir: storageDir}}