refactor: keyboard nav as primary feature, design tweaks behind experimental toggle

content/settings-defaults.js

@@ -4,6 +4,12 @@
 window.OutlookRelook = window.OutlookRelook || {};
 
 window.OutlookRelook.DEFAULTS = {
+  // Keyboard Navigation (primary feature, always visible)
+  keyboardMultiSelect: true,
+
+  // Design Tweaks (experimental, hidden by default)
+  enableDesignTweaks: false,
+
   // Theme & Appearance
   theme: 'swiss',
   colorScheme: 'system',    // 'light' | 'dark' | 'system'
@@ -53,9 +59,6 @@ window.OutlookRelook.DEFAULTS = {
   autoResizeCompose: true,
   throttleNotifications: false,
 
-  // Keyboard Navigation
-  keyboardMultiSelect: true,
-
   // Quick Actions
   markAllReadButton: true,
   quickFolderJump: true,