Correctly respond with 404

app/action.rb

@@ -40,6 +40,7 @@ module Adamantium
     end
 
     def not_found(_req, res, _exception)
+      res.status = 404
       res.render not_found_view
     end
 

app/actions/pages/show.rb

@@ -7,6 +7,7 @@ module Adamantium
         def handle(req, res)
           slug = req.params[:slug]
 
+          res.status = File.exist?("app/content/pages/#{slug}.md") ? 200 : 404
           res.render show, slug: slug
         end
       end