extract shared theme CSS into standalone bundle

Move the 3 theme layer imports (primitives, layer2-attributes, semantic)
out of admin.css and shop.css into a new theme.css bundle loaded by all
root layouts. Eliminates 28 KB of duplication on admin pages where both
admin.css and shop.css were each embedding the same theme CSS.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/css/admin.css

@@ -3,11 +3,6 @@
 /* Reset */
 @import "./admin/reset.css";
 
-/* Theme CSS layers (used by theme editor preview) */
-@import "./theme-primitives.css";
-@import "./theme-layer2-attributes.css";
-@import "./theme-semantic.css";
-
 /* Admin components, layout, icons, transitions */
 @import "./admin/components.css";
 @import "./admin/layout.css";

assets/css/shop.css

@@ -5,13 +5,6 @@
 
 @import "./shop/reset.css";
 
-/* Theme CSS — unlayered so it overrides component layers (intentional).
-   Primitives set CSS custom properties, layer2 sets theme-aware rules,
-   semantic sets base styles on .themed containers. */
-@import "./theme-primitives.css";
-@import "./theme-layer2-attributes.css";
-@import "./theme-semantic.css";
-
 @import "./shop/components.css";
 @import "./shop/layout.css";
 @import "./shop/utilities.css";

assets/css/theme.css

@@ -0,0 +1,6 @@
+/* Theme design tokens — shared by admin and shop CSS bundles.
+   Loaded separately so the browser caches it once for all page types. */
+
+@import "./theme-primitives.css";
+@import "./theme-layer2-attributes.css";
+@import "./theme-semantic.css";

config/config.exs

@@ -61,6 +61,10 @@ config :esbuild,
   berrypod_admin_css: [
     args: ~w(css/admin.css --bundle --outdir=../priv/static/assets/css),
     cd: Path.expand("../assets", __DIR__)
+  ],
+  berrypod_theme_css: [
+    args: ~w(css/theme.css --bundle --outdir=../priv/static/assets/css),
+    cd: Path.expand("../assets", __DIR__)
   ]
 
 # Configures Elixir's Logger

config/dev.exs

@@ -35,7 +35,9 @@ config :berrypod, BerrypodWeb.Endpoint,
     esbuild_shop_css:
       {Esbuild, :install_and_run, [:berrypod_shop_css, ~w(--sourcemap=inline --watch)]},
     esbuild_admin_css:
-      {Esbuild, :install_and_run, [:berrypod_admin_css, ~w(--sourcemap=inline --watch)]}
+      {Esbuild, :install_and_run, [:berrypod_admin_css, ~w(--sourcemap=inline --watch)]},
+    esbuild_theme_css:
+      {Esbuild, :install_and_run, [:berrypod_theme_css, ~w(--sourcemap=inline --watch)]}
   ]
 
 # ## SSL Support

lib/berrypod_web/components/layouts/admin_root.html.heex

@@ -18,6 +18,7 @@
     <style>
       @layer properties, reset, primitives, tokens, theme, base, components, layout, admin, utilities, overrides;
     </style>
+    <link phx-track-static rel="stylesheet" href={~p"/assets/css/theme.css"} />
     <link phx-track-static rel="stylesheet" href={~p"/assets/css/admin.css"} />
     <link phx-track-static rel="stylesheet" href={~p"/assets/css/shop.css"} />
     <!-- Generated theme CSS with @font-face declarations -->

lib/berrypod_web/components/layouts/root.html.heex

@@ -18,6 +18,7 @@
     <style>
       @layer properties, reset, primitives, tokens, theme, base, components, layout, admin, utilities, overrides;
     </style>
+    <link phx-track-static rel="stylesheet" href={~p"/assets/css/theme.css"} />
     <link phx-track-static rel="stylesheet" href={~p"/assets/css/admin.css"} />
     <!-- Generated theme CSS with @font-face declarations -->
     <style id="theme-css">

lib/berrypod_web/components/layouts/shop_root.html.heex

@@ -62,6 +62,7 @@
     <style>
       @layer properties, reset, primitives, tokens, theme, base, components, layout, utilities, overrides;
     </style>
+    <link phx-track-static rel="stylesheet" href={~p"/assets/css/theme.css"} />
     <link phx-track-static rel="stylesheet" href={~p"/assets/css/shop.css"} />
     <%= if assigns[:current_scope] && @current_scope.user do %>
       <link phx-track-static rel="stylesheet" href={~p"/assets/css/admin.css"} />

mix.exs

@@ -100,12 +100,14 @@ defmodule Berrypod.MixProject do
         "compile",
         "esbuild berrypod",
         "esbuild berrypod_shop_css",
-        "esbuild berrypod_admin_css"
+        "esbuild berrypod_admin_css",
+        "esbuild berrypod_theme_css"
       ],
       "assets.deploy": [
         "esbuild berrypod --minify",
         "esbuild berrypod_shop_css --minify",
         "esbuild berrypod_admin_css --minify",
+        "esbuild berrypod_theme_css --minify",
         "phx.digest"
       ],
       precommit: ["compile --warning-as-errors", "deps.unlock --unused", "format", "test"],

test/berrypod_web/live/theme_css_consistency_test.exs

@@ -90,11 +90,11 @@ defmodule BerrypodWeb.ThemeCSSConsistencyTest do
   end
 
   describe "CSS file structure" do
-    test "admin.css imports shared theme layers" do
+    test "theme.css imports shared theme layers" do
-      css_path = Path.join([File.cwd!(), "assets", "css", "admin.css"])
+      css_path = Path.join([File.cwd!(), "assets", "css", "theme.css"])
       css_content = File.read!(css_path)
 
-      # Admin imports the shared theme layers so .themed resolves all tokens
+      # Theme bundle imports all three shared layers
       assert css_content =~ "theme-primitives.css"
       assert css_content =~ "theme-layer2-attributes.css"
       assert css_content =~ "theme-semantic.css"