fix: Hide output panel in analytics mode to prevent overlay

Analytics is a sidebar-only mode with no visuals container, so the
output panel was rendering on top of the analytics content. Add
analytics-active class to expand the sidebar full-width and hide
the output panel when in analytics mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/index.html

@@ -3818,6 +3818,8 @@
                 } else {
                     mainContent.classList.remove('mesh-sidebar-hidden');
                 }
+                // Analytics is sidebar-only — hide output panel and expand sidebar
+                mainContent.classList.toggle('analytics-active', mode === 'analytics');
             }
 
             // Show/hide mode-specific timeline containers