Restore compact Changes diff controls (#1945)

* feat(app): restore compact Changes diff controls

Keep the folder tree behind a view toggle while preserving the flat file list as the default.

Move secondary diff options into the overflow menu so the Changes toolbar stays compact.

* fix(app): mirror whitespace diff option copy

* fix(app): polish diff controls review follow-up

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

@@ -719,7 +719,13 @@ export const ja: TranslationResources = {
         tooLarge: "差分が大きすぎて表示できません",
         unified: "ユニファイド差分",
         split: "左右比較",
+        switchToUnified: "ユニファイド差分に切り替え",
+        switchToSplit: "左右比較差分に切り替え",
+        showTreeView: "フォルダツリーを表示",
+        showFlatView: "フラットなファイル一覧を表示",
+        options: "差分オプション",
         hideWhitespace: "空白を非表示",
+        showWhitespace: "空白を表示",
         scrollLongLines: "長い行をスクロール",
         wrapLongLines: "長い行を折り返す",
         collapseAll: "すべて折りたたむ",