Fix ordering of PDF preview layers (#13132)

GitOrigin-RevId: 1f9429f7e760035377990b12ce9ef8c39b3d0534

services/web/frontend/stylesheets/app/editor/logs.less

@@ -3,6 +3,7 @@
   top: @pdf-top-offset;
   overflow-y: auto;
   background-color: @logs-pane-bg;
+  z-index: 11; // above the PDF viewer + controls
 }
 
 .logs-pane-content {

services/web/frontend/stylesheets/app/editor/pdf.less

@@ -213,7 +213,7 @@
     top: 0;
     left: 0;
     display: inline-block;
-    z-index: 2;
+    z-index: 10; // above the PDF viewer
     .btn-group {
       transition: opacity 0.5s ease, visibility 0 linear 0.5s;
       visibility: hidden;