sync editor state with URL for browser back support

- add ?edit=page/theme/settings param when opening editor or switching tabs
- remove ?edit param when closing editor
- restore .themed class on shop_root for editor panel background tokens
- collapse editor when navigating back to URL without ?edit param

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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

@@ -80,8 +80,9 @@
         This shop works without JavaScript, but some features work better with it enabled.
       </div>
     </noscript>
-    <%!-- Data attributes live on .shop-container inside LiveView for live updates --%>
-    <div class="shop-root">
+    <%!-- .themed here provides fallback theme tokens; .shop-container.themed inside
+         LiveView has data attributes for live updates --%>
+    <div class="shop-root themed">
       {@inner_content}
     </div>
   </body>

lib/berrypod_web/page_editor_hook.ex

@@ -18,7 +18,7 @@ defmodule BerrypodWeb.PageEditorHook do
   """
 
   import Phoenix.Component, only: [assign: 3]
-  import Phoenix.LiveView, only: [attach_hook: 4, push_navigate: 2]
+  import Phoenix.LiveView, only: [attach_hook: 4, push_navigate: 2, push_patch: 2]
 
   alias Berrypod.{Media, Settings}
   alias Berrypod.Pages
@@ -119,7 +119,12 @@ defmodule BerrypodWeb.PageEditorHook do
             |> assign(:editor_active_tab, :settings)
             |> maybe_enter_theme_mode()
 
+          nil ->
+            # No edit param - collapse the editor (supports browser back)
+            assign(socket, :editor_sheet_state, :collapsed)
+
           _ ->
+            # Unknown edit value - ignore
             socket
         end
       end
@@ -175,12 +180,30 @@ defmodule BerrypodWeb.PageEditorHook do
   defp handle_editor_event("editor_set_sheet_state", %{"state" => state_str}, socket) do
     if socket.assigns.is_admin do
       state = if state_str == "open", do: :open, else: :collapsed
-      {:halt, assign(socket, :editor_sheet_state, state)}
+
+      socket =
+        socket
+        |> assign(:editor_sheet_state, state)
+        |> sync_edit_url_param(state)
+
+      {:halt, socket}
     else
       {:cont, socket}
     end
   end
 
+  # Sync URL ?edit param with editor state
+  defp sync_edit_url_param(socket, :collapsed) do
+    path = socket.assigns.editor_current_path || "/"
+    push_patch(socket, to: path)
+  end
+
+  defp sync_edit_url_param(socket, :open) do
+    path = socket.assigns.editor_current_path || "/"
+    tab = socket.assigns.editor_active_tab
+    push_patch(socket, to: "#{path}?edit=#{tab}")
+  end
+
   # Tab switching for unified editor
   defp handle_editor_event("editor_set_tab", %{"tab" => tab_str}, socket) do
     if socket.assigns.is_admin do
@@ -228,6 +251,12 @@ defmodule BerrypodWeb.PageEditorHook do
             assign(socket, :editor_active_tab, :settings)
         end
 
+      # Open the sheet and sync URL with new tab
+      socket =
+        socket
+        |> assign(:editor_sheet_state, :open)
+        |> sync_edit_url_param(:open)
+
       {:halt, socket}
     else
       {:cont, socket}