Language policy rule (always loaded)

The project targets a global audience and is English-first.

Code, comments, docstrings, docs, commit messages, identifiers: English only.
CJK characters are allowed only in:
- test fixtures under tests/ and data/ (multilingual input is the point), and
- locale-suffixed mirror files (e.g. *_zh.json).
Do not introduce CJK into src/, docs/, or config.

Enforcement: make check-cjk scans for stray CJK outside the allowlist (advisory). Keep user-facing strings and error messages in English.