fix: no-all-caps-body-text false positive on CJK text

[skoshx]

Summary

Fixes no-all-caps-body-text false positive on Japanese, Chinese, Korean, and Arabic text (caseless scripts).

Closes #1429

Root Cause

The rule's detection logic treated any text without lowercase letters as "all caps":

const isLiteralUppercase = !LOWERCASE_LETTER_PATTERN.test(staticText);

For CJK scripts (Japanese, Chinese, Korean) and Arabic, which have no letter case, this condition is always true. Every long paragraph in these languages was incorrectly flagged as all-caps body copy, with no actionable fix (there is no "sentence case" for caseless scripts).

The Fix

Changed the logic to require actual uppercase letters before considering text "all caps":

const hasUppercase = UPPERCASE_LETTER_PATTERN.test(staticText);
const hasLowercase = LOWERCASE_LETTER_PATTERN.test(staticText);
const isLiteralUppercase = hasUppercase && !hasLowercase;

Now:

• Caseless scripts (CJK, Arabic, etc.) are skipped entirely
• Latin text in all caps is still caught correctly
• Mixed-script text is only flagged if the cased portion is all uppercase

Scope

This fix is deliberately narrow and conservative:

• Only changes the "literal uppercase" detection logic
• Does not touch the hasUppercaseStyle() check (CSS text-transform: uppercase detection)
• Makes the rule MORE conservative (fewer false positives, no new false negatives)

Testing

Added comprehensive unit tests covering:

• Japanese (Hiragana/Katakana/Kanji)
• Chinese (Simplified characters)
• Korean (Hangul)
• Arabic
• Mixed-script text (English + Japanese)
• Edge case: mixed script where only the English portion is all-caps (correctly flagged)

All existing tests pass.

Parity

Could not run rde parity due to schema version mismatch in the eval environment (expecting v1, current is v3). However:

• The fix is highly targeted (one detection condition)
• Makes the rule more conservative (reduces findings, doesn't add new ones)
• No possibility of introducing false positives elsewhere
• Comprehensive unit tests cover the edge cases

Changeset

Added patch-level changeset for oxlint-plugin-react-doctor.