Reach the Irb through Context#irb in commands again

Context#irb is always the Irb running the command, so injecting it
separately added an API without changing behavior.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0175QjMQGeUPByLSqoL6ye5U

Author: claude

lib/irb.rb

@@ -248,7 +248,7 @@ def evaluate_statement(statement, line_no) # :nodoc:
         result = @context.evaluate_expression(statement.code, line_no)
         @context.set_last_value(result)
       when Statement::Command
-        statement.command_class.execute(@context, statement.arg, irb: self)
+        statement.command_class.execute(@context, statement.arg)
       when Statement::IncorrectAlias
         warn statement.message
       end

lib/irb/command/base.rb

@@ -31,8 +31,8 @@ def help_message(help_message = nil)
           @help_message
         end
 
-        def execute(irb_context, arg, irb: nil)
-          new(irb_context, irb: irb).execute(arg)
+        def execute(irb_context, arg)
+          new(irb_context).execute(arg)
         rescue CommandArgumentError => e
           puts e.message
         end
@@ -79,19 +79,12 @@ def wrap_lines(text, width)
         end
       end
 
-      def initialize(irb_context, irb: nil)
+      def initialize(irb_context)
         @irb_context = irb_context
-        @irb = irb
       end
 
       attr_reader :irb_context
 
-      # The Irb running this command. Falls back to Context#irb for commands
-      # executed outside of Irb's loop.
-      def irb
-        @irb || irb_context.irb
-      end
-
       def execute(arg)
         #nop
       end

lib/irb/command/debug.rb

@@ -41,7 +41,7 @@ def execute_debug_command(pre_cmds: nil, do_cmds: nil)
             return
           end
 
-          unless IRB::Debug.setup(irb)
+          unless IRB::Debug.setup(irb_context.irb)
             puts <<~MSG
               You need to install the debug gem before using this command.
               If you use `bundle exec`, please add `gem "debug"` into your Gemfile.

lib/irb/context.rb

@@ -251,10 +251,7 @@ def main
     # context is created. See ::new for more # information on +input_method+.
     attr_accessor :io
 
-    # The Irb that owns this context.
-    #
-    # Prefer not to depend on this: commands get the Irb running them through
-    # Command::Base#irb.
+    # Current irb session.
     attr_accessor :irb
     # A copy of the default <code>IRB.conf[:AP_NAME]</code>
     attr_accessor :ap_name

lib/irb/ext/loader.rb

@@ -39,6 +39,7 @@ def search_file_from_ruby_path(fn) # :nodoc:
     #
     # See Irb#suspend_input_method for more information.
     def source_file(path)
+      irb = irb_context.irb
       irb.suspend_name(path, File.basename(path)) do
         FileInputMethod.open(path) do |io|
           irb.suspend_input_method(io) do
@@ -63,6 +64,7 @@ def source_file(path)
     #
     # See Irb#suspend_input_method for more information.
     def load_file(path, priv = nil)
+      irb = irb_context.irb
       irb.suspend_name(path, File.basename(path)) do
 
         if priv