Fix yamatanooroti test failures from startup banner

- Suppress banner when `-f` flag is used (RC=false)
- Disable banner in yamatanooroti test setup via irbrc
- Prepend banner disable in write_irbrc helper

Author: st0012

lib/irb.rb

@@ -597,6 +597,7 @@ def inspect
     private
 
     def show_startup_message?
+      return false unless IRB.conf[:RC]
       return false unless IRB.conf.fetch(:SHOW_BANNER, true)
       return true if ENV['TEST_IRB_FORCE_INTERACTIVE']
 

test/irb/yamatanooroti/test_rendering.rb

@@ -26,6 +26,7 @@ def setup
     @irbrc_backup = ENV['IRBRC']
     @irbrc_file = ENV['IRBRC'] = File.join(@tmpdir, 'temporaty_irbrc')
     File.unlink(@irbrc_file) if File.exist?(@irbrc_file)
+    File.write(@irbrc_file, "IRB.conf[:SHOW_BANNER] = false\n")
     ENV['HOME'] = File.join(@tmpdir, 'home')
     ENV['XDG_CONFIG_HOME'] = File.join(@tmpdir, 'xdg_config_home')
   end
@@ -520,6 +521,7 @@ def test_debug_integration_doesnt_hint_debugger_commands_in_nomultiline_mode
 
   def write_irbrc(content)
     File.open(@irbrc_file, 'w') do |f|
+      f.write "IRB.conf[:SHOW_BANNER] = false\n"
       f.write content
     end
   end