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

template.html

@@ -53,6 +53,9 @@
                     <!-- Content will be populated by JavaScript -->
                 </div>
 
+                <!-- Divider after Inventory -->
+                <div id="rpg-divider-inventory" class="rpg-divider"></div>
+
                 <!-- Quests Section -->
                 <div id="rpg-quests" class="rpg-section rpg-quests-section">
                     <!-- Content will be populated by JavaScript -->
@@ -182,6 +185,11 @@
                     <span data-i18n-key="template.settingsModal.display.showInventory">Show Inventory</span>
                 </label>
 
+                <label class="checkbox_label">
+                    <input type="checkbox" id="rpg-toggle-quests" />
+                    <span data-i18n-key="template.settingsModal.display.showQuests">Show Quests</span>
+                </label>
+
                 <label class="checkbox_label">
                     <input type="checkbox" id="rpg-toggle-thoughts-in-chat" />
                     <span data-i18n-key="template.settingsModal.display.showThoughtsInChat">Show Thoughts in Chat</span>