fix: Improved compact mode for multiple toolbar, b=(no-bug), c=compact-mode, tabs

src/zen/compact-mode/ZenCompactMode.mjs

@@ -271,6 +271,8 @@ var gZenCompactModeManager = {
               // Subtract from the splitter width to end up with the correct element separation
               sidebarWidth += 1.5 * splitterWidth - elementSeparation;
             }
+          } else {
+            sidebarWidth -= elementSeparation;
           }
           gZenUIManager.motion
             .animate(

src/zen/compact-mode/zen-compact-mode.css

@@ -64,10 +64,14 @@
           top: 0;
           bottom: var(--zen-element-separation);
           padding: 0 var(--zen-compact-float) !important;
-
+          :root[zen-single-toolbar='true'] & {
             top: calc(var(--zen-element-separation) / 2);
             height: calc(100% - var(--zen-element-separation));
-
+          }
+          :root:not([zen-single-toolbar='true']) & {
+            height: calc(100% + var(--zen-element-separation) * 2);
+            top: calc(var(--zen-element-separation) / -2);
+          }
           & #zen-sidebar-top-buttons {
             margin: 0 0 calc(var(--zen-toolbox-padding) / 2) 0;
           }

src/zen/tabs/zen-tabs/vertical-tabs-topbuttons-fix.css

@@ -4,7 +4,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
-&
+&:not([zen-compact-animating])
   #zen-sidebar-top-buttons:not(
     :has(#zen-sidebar-top-buttons-customization-target > *:not(#zen-sidebar-top-buttons-separator))
   ) {