FIX: Flex behavior should shrink header items instead of brand

Fixes issue #1143

Author: bheberlein

src/pydata_sphinx_theme/assets/styles/components/header/_header-logo.scss

@@ -6,6 +6,7 @@
   width: auto;
   margin: 0;
   display: flex;
+  flex-shrink: 0;
   align-items: center;
   gap: 0.5rem;
 

src/pydata_sphinx_theme/assets/styles/sections/_header.scss

@@ -30,6 +30,7 @@
   // Hide the header items on mobile
   .navbar-header-items {
     display: none;
+    flex-shrink: 1;
     @include media-breakpoint-up($breakpoint-sidebar-primary) {
       display: flex;
       flex-grow: 1;
@@ -52,6 +53,7 @@
 
   // A little smaller because this is displayed by default on mobile
   #navbar-start {
+    flex-shrink: 0;
     margin-right: auto;
     gap: 0.5rem;
   }