rules/zh shipped ~17KB of Chinese rule text into the auto-loaded rules tree
of every default install (rules-core installs the bare 'rules' path with
defaultInstall: true), with no paths: frontmatter gating. The content had
also drifted behind both rules/common and the maintained translations in
docs/zh-CN/rules/common (e.g. zh/coding-style.md 48 lines vs the 52-line
docs/zh-CN copy), and 'zh' was already dropped from the installer's language
help in favor of the gated docs-zh-cn locale module (--locale zh-CN).
- move rules/zh/code-review.md to docs/zh-CN/rules/common/code-review.md:
the only file with no counterpart in the maintained locale tree (fills a
zh-CN parity gap with rules/common/code-review.md)
- delete the remaining 10 rules/zh files, all older duplicates of
docs/zh-CN/rules/common content
- update trae-install test to assert the rules tree via rules/web instead
Not addressed here: rules/README.md (~5.5KB of installer docs) still ships
into the auto-loaded tree via the bare 'rules' module path; filtering README
files from rule-tree expansion is a separate decision
