feat: Add sidebar style options to appearance settings

- Introduced a new section in the Appearance settings to allow users to choose between 'unified' and 'discord' sidebar layouts.
- Updated the app state and settings migration to include the new sidebarStyle property.
- Enhanced the UI to reflect the selected sidebar style with appropriate visual feedback.
- Ensured synchronization of sidebar style settings across the application.

apps/ui/src/hooks/use-settings-migration.ts

@@ -698,6 +698,7 @@ export function hydrateStoreFromSettings(settings: GlobalSettings): void {
     fontFamilySans: settings.fontFamilySans ?? null,
     fontFamilyMono: settings.fontFamilyMono ?? null,
     sidebarOpen: settings.sidebarOpen ?? true,
+    sidebarStyle: settings.sidebarStyle ?? 'unified',
     chatHistoryOpen: settings.chatHistoryOpen ?? false,
     maxConcurrency: settings.maxConcurrency ?? DEFAULT_MAX_CONCURRENCY,
     autoModeByWorktree: restoredAutoModeByWorktree,

apps/ui/src/hooks/use-settings-sync.ts

@@ -53,6 +53,7 @@ const SETTINGS_FIELDS_TO_SYNC = [
   'terminalFontFamily', // Maps to terminalState.fontFamily
   'openTerminalMode', // Maps to terminalState.openTerminalMode
   'sidebarOpen',
+  'sidebarStyle',
   'chatHistoryOpen',
   'maxConcurrency',
   'autoModeByWorktree', // Per-worktree auto mode settings (only maxConcurrency is persisted)
@@ -697,6 +698,7 @@ export async function refreshSettingsFromServer(): Promise<boolean> {
     useAppStore.setState({
       theme: serverSettings.theme as unknown as ThemeMode,
       sidebarOpen: serverSettings.sidebarOpen,
+      sidebarStyle: serverSettings.sidebarStyle ?? 'unified',
       chatHistoryOpen: serverSettings.chatHistoryOpen,
       maxConcurrency: serverSettings.maxConcurrency,
       autoModeByWorktree: restoredAutoModeByWorktree,