Drop stale exe/pppkg ignore from .standard.yml

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EiyJC73Mz8xZyCTvCEY8qn

.standard.yml

@@ -5,5 +5,3 @@ ignore:
   # Fixtures are deliberately malformed or copied verbatim from elsewhere;
   # linting them defeats the point of having them.
   - "test/files/**/*"
-  # The pre-refactor monolith, kept only for reference.
-  - "exe/pppkg"