Refactor CSS styles for Zen browser UI and tabs

- Update the max-width property for #zen-appcontent-wrapper in zen-browser-ui.css to ensure it takes up the full width.
- Remove the label display for toolbar buttons in zen-glance.css to improve the visual appearance.
- Hide the new tab button in vertical-tabs.css to align with the Zen browser UI design.

src/browser/base/content/browser-box-inc-xhtml.patch

@@ -1,12 +1,12 @@
 diff --git a/browser/base/content/browser-box.inc.xhtml b/browser/base/content/browser-box.inc.xhtml
-index 7f71abe7d80e4c09dd088517ec9ef106c7cb8654..d094aeb36e1595d4d28d518654fb3ba848003c91 100644
+index 7f71abe7d80e4c09dd088517ec9ef106c7cb8654..281a3716d56edda243bfca7ebbe0797d75c844e7 100644
 --- a/browser/base/content/browser-box.inc.xhtml
 +++ b/browser/base/content/browser-box.inc.xhtml
 @@ -22,7 +22,13 @@
      <browser id="sidebar" autoscroll="false" disablehistory="true" disablefullscreen="true" tooltip="aHTMLTooltip"/>
    </vbox>
    <splitter id="sidebar-splitter" class="chromeclass-extrachrome sidebar-splitter" resizebefore="sibling" resizeafter="none" hidden="true"/>
-+<vbox flex="1">
++<vbox flex="1" id="zen-appcontent-wrapper">
 +<html:div id="zen-appcontent-navbar-container"></html:div>
 +<hbox id="zen-tabbox-wrapper" flex="1">
    <tabbox id="tabbrowser-tabbox" flex="1" tabcontainer="tabbrowser-tabs">

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

@@ -73,6 +73,10 @@
   }
 }
 
+#zen-appcontent-wrapper {
+  max-width: 100%;
+}
+
 #tabbrowser-tabbox {
   display: flex;
   flex-direction: row;

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

@@ -111,6 +111,10 @@
         & toolbarbutton {
           width: 32px;
           height: 32px;
+
+          & label {
+            display: none;
+          }
         }
       }
 

src/browser/base/content/zen-styles/zen-tabs/vertical-tabs.css

@@ -733,6 +733,10 @@
     }
   }
 
+  #tabs-newtab-button {
+    display: none;
+  }
+
   @media (-moz-bool-pref: 'zen.tabs.show-newtab-under') {
     #tabs-newtab-button {
       display: flex !important;