style: adopt ruff (format + lint) at 88, replacing black/isort/flake8

Format-only: Python files are AST-identical apart from import order.
pre-commit end-of-file/trailing-whitespace fixes applied repo-wide.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.gitignore

@@ -3,4 +3,3 @@ dist
 *.egg-info
 __pycache__
 .idea
-