Rescue Errno::ENOENT in system-test entrypoint controller

The Rails 8.1 CI cell intermittently fails ViewComponentSystemTest with
Ferrum::PendingConnectionsError. Traced to validate_file_path raising
Errno::ENOENT from File.realpath when the browser issues a late
request (favicon retry, teardown screenshot) after
with_rendered_component_path's ensure block has unlinked the temp file.

Rescue Errno::ENOENT the same way we already rescue nefarious-path
errors: return 404. The pending late request completes cleanly instead
of cascading into a Ferrum timeout during teardown.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: joelhawksley

app/controllers/view_components_system_test_controller.rb

@@ -11,6 +11,7 @@ def self.temp_dir
     end
 
     rescue_from ViewComponent::SystemTestControllerNefariousPathError, with: :render_not_found
+    rescue_from Errno::ENOENT, with: :render_not_found
 
     def system_test_entrypoint
       render file: @path