fix(#1463): Remove duplicate atlas-toggle-btn from index.html

Merge artifact left a partial <button id="atlas-toggle-btn">
with no closing tag at line 168. The real atlas button at
line 176 (title="Portal Atlas") has proper content.

Removed the duplicate. Verified:
  - 1 atlas-toggle-btn (was 2)
  - 0 conflict markers
  - 0 other duplicate IDs

Closes #1463, #1336

index.html

@@ -165,7 +165,6 @@
 
   <!-- Top Right: Agent Log, Atlas & SOUL Toggle -->
   <div class="hud-top-right">
-    <button id="atlas-toggle-btn" class="hud-icon-btn" title="World Directory">
     <button id="soul-toggle-btn" class="hud-icon-btn" title="Timmy's SOUL">
       <span class="hud-icon">✦</span>
       <span class="hud-btn-label">SOUL</span>