Archive finished subagents across the whole track (#3368)

* feat(app): archive finished subagents together

Make the track action clean up finished managed and provider-owned children as one operation while preserving running work. Managed archives remain sequential and provider-owned dismissal stays client-local.

* test(app): clarify subagent archive assertions

packages/app/src/i18n/resources/ar.ts

@@ -1618,6 +1618,7 @@ export const ar: TranslationResources = {
     archiveTooltip: "أرشفة الوكيل الفرعي",
     archiveFinishedAction: "أرشفة الوكلاء الفرعيين المكتملين",
     archiveFinishedTooltip: "أرشفة المكتملين",
+    archiveFinishedRetry: "إعادة المحاولة ({{failed}}/{{total}})",
   },
   panels: {
     draft: {