Merge pull request #2109 from basecamp/theme-tweak

Apply theme preference before body renders

app/views/layouts/_theme_preference.html.erb

@@ -0,0 +1,6 @@
+<%= javascript_tag nonce: true do %>
+  const theme = localStorage.getItem("theme")
+  if (theme && theme !== "auto") {
+    document.documentElement.dataset.theme = theme
+  }
+<% end %>

app/views/layouts/shared/_head.html.erb

@@ -15,6 +15,7 @@
 
   <% turbo_refreshes_with method: :morph, scroll: :preserve %>
 
+  <%= render "layouts/theme_preference" %>
   <%= stylesheet_link_tag :app, "data-turbo-track": "reload" %>
   <%= javascript_importmap_tags %>