feat(inventory): wire up v2 system to main panel with full interactivity

- Add inventory section to template.html between Thoughts and bottom controls
- Wire up renderInventory() to all event handlers (message received, character changed, swipes)
- Initialize inventory container reference and event listeners in index.js
- Add showInventory toggle checkbox to settings with visibility control
- Update layout.js to handle inventory section and divider visibility
- Add renderInventory parameter to updateRPGData for separate mode support
- Update state.js and config.js with inventory container and showInventory setting

Inventory is now fully integrated as a visible, interactive panel section that persists across all user interactions.

template.html

@@ -44,6 +44,14 @@
                 <div id="rpg-thoughts" class="rpg-section rpg-thoughts-section">
                     <!-- Content will be populated by JavaScript -->
                 </div>
+
+                <!-- Divider after Thoughts -->
+                <div id="rpg-divider-thoughts" class="rpg-divider"></div>
+
+                <!-- Inventory Section -->
+                <div id="rpg-inventory" class="rpg-section rpg-inventory-section">
+                    <!-- Content will be populated by JavaScript -->
+                </div>
             </div>
 
             <!-- HTML Prompt Toggle -->
@@ -159,6 +167,11 @@
                     <span>Show Present Characters</span>
                 </label>
 
+                <label class="checkbox_label">
+                    <input type="checkbox" id="rpg-toggle-inventory" />
+                    <span>Show Inventory</span>
+                </label>
+
                 <label class="checkbox_label">
                     <input type="checkbox" id="rpg-toggle-thoughts-in-chat" />
                     <span>Show Thoughts in Chat</span>