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/ja.ts

@@ -190,6 +190,7 @@ export const ja: TranslationResources = {
   agentStream: {
     empty: "このエージェントとチャットを始めましょう...",
     scrollToBottom: "下にスクロール",
+    historyLoadFailed: "エージェントの履歴を読み込めませんでした",
     permission: {
       plan: "プラン",
       required: "権限が必要です",
@@ -1796,6 +1797,10 @@ export const ja: TranslationResources = {
       detailLevel: {
         title: "詳細レベル",
       },
+      chatOutline: {
+        title: "チャットのアウトライン",
+        description: "プロンプト間を移動するためのアウトラインを表示します",
+      },
       fonts: {
         title: "フォント",
         systemDefault: "システムデフォルト",