Refactor CLI to use Ruby stdlib OptionParser

[Copilot]

Replaces the manual argument parsing in the CLI with Ruby's standard library OptionParser for cleaner, more maintainable code.

Changes

The previous implementation used manual string matching and ARGV manipulation:

if ARGV.include?("--help") || ARGV.include?("-h")
  puts help_message
elsif ARGV.include?("--locale") 
  # Manual index finding and deletion
  index = ARGV.index("--locale")
  locale = ARGV.delete_at(index + 1)
  ARGV.delete_at(index)
  options[:locale] = locale
end

Now uses Ruby's standard OptionParser for declarative option definitions:

parser = OptionParser.new do |opts|
  opts.on("-l", "--locale LOCALE", "Uses the provided locale") do |locale|
    options[:locale] = locale
  end
end

Benefits

• Cleaner code: Declarative option definitions instead of manual parsing
• Better error handling: Automatic error messages for invalid options and missing arguments
• Standard Ruby idioms: Uses stdlib patterns familiar to Ruby developers
• Easier maintenance: Adding new options requires just one line instead of complex logic
• Automatic help formatting: OptionParser generates consistent help output

Backward Compatibility

All existing CLI functionality remains identical:

• All short and long options work exactly the same (-h, --help, -v, --version, etc.)
• Error handling behavior is preserved
• All 21 existing tests pass, including 7 CLI-specific tests

This is a pure refactoring with no breaking changes to the public interface.

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