[Bug Fix] Mount ToastRegion in DocsLayout

DocsController uses DocsLayout, not ApplicationLayout — without this,
the Region was missing on every /docs/* page, so window.RubyUI.toast
was never registered (Toaster Stimulus controller never connected) and
Turbo Stream appends had no target.

Author: djalmaaraujo

docs/app/views/layouts/docs_layout.rb

@@ -23,6 +23,7 @@ def view_template(&block)
             end
             render Shared::Footer.new
             render Shared::Flashes.new(notice: flash[:notice], alert: flash[:alert])
+            render RubyUI::ToastRegion.new
           end
         end
       end