Add chapter checkpoint UI improvements and separate Quests toggle

- Fix checkpoint button display with expandMessageActions setting
- Add body class observer to update buttons when setting toggles
- Add cleanupCheckpointUI function for extension disable
- Separate Quests from Inventory with independent toggle
- Add horizontal scrolling to Info Box dashboard
- Add divider between Inventory and Quests sections

src/systems/rendering/quests.js

@@ -160,7 +160,7 @@ export function renderOptionalQuestsView(optionalQuests) {
  * Main render function for quests
  */
 export function renderQuests() {
-    if (!extensionSettings.showInventory || !$questsContainer) {
+    if (!extensionSettings.showQuests || !$questsContainer) {
         return;
     }