fix: remove New Session tab from header

The gear icon for app settings was already added, but the old New Session
tab was not removed. Users can still create sessions via Ctrl+N or other UI elements.

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

src/web/public/index.html

@@ -22,9 +22,6 @@
 
       <!-- Session Tabs -->
       <div class="session-tabs" id="sessionTabs">
-        <div class="session-tab new-tab" onclick="app.createNewSession()" title="New Session (Ctrl+N)">
-          <span>+</span>
-        </div>
       </div>
 
       <div class="header-right">