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/zh-CN.ts

@@ -701,7 +701,13 @@ export const zhCN: TranslationResources = {
         tooLarge: "Diff 过大，无法显示",
         unified: "Unified diff",
         split: "Side-by-side diff",
+        switchToUnified: "切换到统一差异视图",
+        switchToSplit: "切换到并排差异视图",
+        showTreeView: "显示文件夹树",
+        showFlatView: "显示平铺文件列表",
+        options: "Diff 选项",
         hideWhitespace: "隐藏空白差异",
+        showWhitespace: "显示空白差异",
         scrollLongLines: "滚动长行",
         wrapLongLines: "自动换行长行",
         collapseAll: "折叠所有文件",