Display command description in doc dialog on tab completion

[st0012]

Summary

Proposed by @elct9620

Screen.Recording.2026-03-09.at.13.04.21.mov

• Refactor show_doc_dialog_proc into smaller focused methods (rdoc_dialog_contents, easter_egg_dialog_contents, command_doc_dialog_contents, dialog_doc_position)
• Introduce DocumentTarget class hierarchy (CommandDocument, MethodDocument) to replace stringly-typed doc namespace returns for commands
• Display command description and help message in the autocomplete doc dialog popup when a command is selected
• Consolidate full-screen doc display into display_document, eliminating duplication between dialog Alt+d paths and perfect-match display
• Move command dialog content rendering to Command::Base.doc_dialog_content so commands own their presentation

[tompng]

Is the intention of using ' ', a single whitespace, is to squeeze spaces in the text?

  -s  Show the super method.
  ↓
  -s Show the super method.

If it's not, how about something like this?

parts = line.strip.split(/(\s+)/)
parts.each do |part|
  # wrap if exceeded
  if current != indent && current.length + part.length > width
    result << current
    current = indent.dup
  end
  # don't add spaces just after indent
  current << part unless current == indent && part.match?(/\A\s+\z/)
end
# needs result.map(&:rstrip)

It will preserve spaces for this case:

Usage: ls [obj] [-g [query]]

  -g [query]  Filter the output with a query.
  -a [aa]     Foo bar
  -b [bbb]    Baz
              ↑ this alignment will be kept

One good part of this: We can flexibly change the regexp such as line.strip.split(/(\s+)|\b/)