fix(styles): update z-index for sidebar splitter and remove min-width from workspace button

src/browser/base/content/zen-styles/zen-sidebar-panels.css

@@ -111,7 +111,7 @@
   background: transparent;
   border: none;
   cursor: ew-resize;
-  z-index: 2;
+  z-index: 3;
 
   &:is(.zen-split-view-splitter[orient='vertical']) {
     /* Bit of a hacky solution, but it works */

src/browser/base/content/zen-styles/zen-workspaces.css

@@ -72,7 +72,6 @@
     &:has(toolbarbutton:hover) toolbarbutton[active='true'] {
       &:not(:hover) {
         width: min(var(--zen-overflowed-workspace-button-width), 25px);
-        min-width: 10px;
 
         &::after {
           content: '';