Show help if you arrow-up but don't have any previous commands yet

- @jorgemanrubia this is a little fragile because it relies on CSS `:empty` which fails if any whitespace is present, which is why I needed to make the `<ul>` a one-liner. If we like this we may want to implement something more robust

app/assets/stylesheets/terminals.css

@@ -78,7 +78,8 @@
   .terminal__help {
     display: none;
 
-    .terminal--showing-help & {
+    .terminal--showing-help &,
+    .terminal--open .terminal__menu:empty ~ & {
       border-block-end: 1px dashed;
       display: block;
       margin-block-end: 0.5lh;

app/views/commands/index.html.erb

@@ -1,7 +1,5 @@
 <%= turbo_frame_tag :recent_commands do %>
-  <ul class="terminal__menu flex-column txt-align-start margin-none margin-block-end unpad" aria-label="Recent commands">
-    <%= render partial: "commands/command", collection: @commands %>
-  </ul>
+  <ul class="terminal__menu flex-column txt-align-start margin-none margin-block-end unpad" aria-label="Recent commands"><%= render partial: "commands/command", collection: @commands %></ul>
 
   <%= render "commands/help" %>
 <% end %>