chore(instructeurs): sections summary only on xl screens

app/components/viewable_champ/header_sections_summary_component.rb

@@ -1,16 +1,18 @@
 class ViewableChamp::HeaderSectionsSummaryComponent < ApplicationComponent
+  attr_reader :header_sections
+
   def initialize(dossier:, is_private:)
     @dossier = dossier
     @is_private = is_private
-  end
 
-  def header_sections
-    @dossier.revision
+    @header_sections = @dossier.revision
       .types_de_champ_for(scope: @is_private ? :private : :public)
       .filter(&:header_section?)
       .map { @dossier.project_champ(_1, nil) } # row_id not needed, do not link to repetiion header_sections
   end
 
+  def render? = header_sections.any?
+
   def href(header_section) # used by viewable champs to anchor elements
     "##{header_section.input_group_id}"
   end