New fixer hook that replaces UTF-8 em-dashes (U+2014) with a plain
hyphen (-), modeled on the trailing-whitespace hook.
- pre_commit_hooks/remove_em_dash.py: the fixer (binary-safe, UTF-8 only)
- tests/remove_em_dash_test.py: full coverage of fix and no-op cases
- registered in setup.cfg, .pre-commit-hooks.yaml, and README.md
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
