[Bug Fix] Exit with non-zero status when components are missing

`validate_components!` used a bare `exit`, which in Ruby is `exit(true)` and
yields exit status 0. A failed generation therefore reported success to the
shell, so CI steps and scripts gating on the exit code treated missing-component
errors as passing runs. Use `exit 1` so the failure is observable.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jacksonpires

gem/lib/generators/ruby_ui/component_generator.rb

@@ -31,7 +31,7 @@ def validate_components!
         return if missing.empty?
 
         say "Component(s) not found: #{missing.join(", ")}", :red
-        exit
+        exit 1
       end
 
       def copy_related_component_files(component_name)