Challenge 2: A Shared Navbar Partial — Solution

<!-- app/views/shared/_navbar.html.erb -->
<nav>
  <%= link_to "Home", root_path %>
  <%= link_to "All Posts", posts_path %>
</nav>

<!-- Line to add in app/views/layouts/application.html.erb, above <%= yield %> -->
<%= render "shared/navbar" %>

=begin
Notes:
- The file itself is named with a leading underscore (_navbar.html.erb),
  marking it as a partial per Rails' convention -- but it's referenced
  without the underscore, as "shared/navbar", exactly as the chapter
  describes.
- Both link_to calls use named route helpers (root_path, posts_path) from
  Chapter 2, generating real <a href="..."> tags rather than hand-written
  HTML strings with interpolated paths.
- Placing <%= render "shared/navbar" %> once in application.html.erb,
  above <%= yield %>, is all that's needed to have the navbar appear on
  every single page in the app automatically -- no individual view needs
  to include it itself, unlike the EJS pattern the chapter contrasted
  this against.
=end