feat(app): add chat outline navigation (#2792)

* feat(app): add chat outline navigation

Long agent sessions need prompt navigation without coupling viewport movement to disposable server windows. Keep fetched timeline pages in client state so repeated jumps stay local, and settle prompt jumps against virtualized row measurement changes.

* fix(app): preserve chat outline timeline coverage

* fix(app): reconcile outline window submissions

* fix(app): harden outline timeline navigation

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

@@ -192,6 +192,7 @@ export const fr: TranslationResources = {
   agentStream: {
     empty: "Commencez à discuter avec cet agent...",
     scrollToBottom: "Faire défiler vers le bas",
+    historyLoadFailed: "Impossible de charger l’historique de l’agent",
     permission: {
       plan: "Plan",
       required: "Autorisation requise",
@@ -1831,6 +1832,10 @@ export const fr: TranslationResources = {
       detailLevel: {
         title: "Niveau de détail",
       },
+      chatOutline: {
+        title: "Plan de la discussion",
+        description: "Afficher un plan pour passer d’une requête à l’autre",
+      },
       fonts: {
         title: "Polices",
         systemDefault: "Valeur par défaut du système",