fix: remove duplicate border-left next to CPU stat

The header-system-stats had its own border-left in addition to the
header-right border-left, creating two vertical lines. Removed the
inner one for a cleaner look.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/web/public/index.html

@@ -38,6 +38,13 @@
             </div>
             <span class="stat-value" id="statCpu">--%</span>
           </div>
+          <div class="stat-item">
+            <span class="stat-label">MEM</span>
+            <div class="stat-bar">
+              <div class="stat-bar-fill stat-bar-mem" id="statMemBar"></div>
+            </div>
+            <span class="stat-value" id="statMem">--</span>
+          </div>
         </div>
         <button class="btn-icon-header btn-notifications" onclick="app.toggleNotifications()" title="Notifications">
           <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M18 8A6 6 0 0 0 6 8c0 7-3 9-3 9h18s-3-2-3-9"/><path d="M13.73 21a2 2 0 0 1-3.46 0"/></svg>

src/web/public/styles.css

@@ -248,8 +248,6 @@ body {
   font-family: 'SF Mono', Monaco, monospace;
   color: var(--text-dim);
   padding: 0 0.5rem;
-  border-left: 1px solid var(--border);
-  margin-left: 0.5rem;
 }
 
 .stat-item {