fix(i18n): exclude unused plural forms from language pack coverage

[chengjie]

What & why

A complete Chinese or Japanese language pack can be reported as partially translated because LanguageRows counts English plural forms that the target locale never selects. For a catalogue containing files and files_one, Chinese needs only files, but currently reports 50% coverage. This also explains why a complete Chinese pack can show 97% in the store dry-run while passing the locale-aware completeness validator.

Use the existing srvtext.Categories CLDR rules to exclude inapplicable catalogue plural forms from both Total and Translated. A suffix is treated as a plural form only when its base key is also in the catalogue, so standalone keys such as standalone_one remain required. Shipped key counts, unknown-key handling, blank-value handling and percentage rounding are preserved. English still requires its singular forms, and shipping unnecessary singular translations cannot inflate coverage.

Type

• Bug fix
• Feature
• Docs
• Refactor / chore

Checklist

• Backend: cd backend && go build ./... && go vet ./... && go test -timeout 30m ./... passes
• Frontend (if touched): pnpm -C packages/core typecheck and the relevant build pass
• Added/updated tests for the change where it makes sense
• Updated docs (docs/, README.md) and CHANGELOG.md if user-facing
• No secrets, credentials or environment-specific hostnames added

Notes for reviewers

• Added regression tests for Chinese, zh-Hans-CN, Japanese, English and Russian, including missing real translations, redundant forms and orphan suffix keys.
• Confirmed the new regression tests fail against unchanged upstream main and pass with this fix.
• go test ./internal/wasmplugin ./internal/srvtext -count=1 -timeout=5m passes. The full backend build/vet/test suite was not run; frontend code is unchanged.
• The store validator will need to use a build containing this fix before its displayed coverage changes.

[brkfun]

Thanks a lot, @chengjie! This is in and ships with filex 0.57.0.

It also takes care of the coverage number the store showed for your pack while we were sorting out #118: once the store's checker runs on 0.57, a complete Chinese pack shows 100%.

And your Chinese language pack is approved and listed in the store now. Thank you for translating filex, and for the careful reports along the way.