refactor: split file.rb into per-class files under lib/dslkeywords/

file.rb was a ~400-line monolith holding seven unrelated classes/modules.
Extract each into its own file so each file has a single responsibility
and stays within the 50-line guideline:

  file_backup.rb  — FileBackup mixin
  symlink.rb      — Symlink class + DSL#symlink
  touch.rb        — Touch class + DSL#touch
  directory.rb    — Directory class + DSL#directory

file.rb keeps BasicFile, BaseFile, File, and DSL#file.
dsl.rb gains explicit require_relative lines for the new files.
No logic was changed; all 29 tests continue to pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions